diff --git a/benchmarks/FfiBoringssl/dart/FfiBoringssl.dart b/benchmarks/FfiBoringssl/dart/FfiBoringssl.dart
index b4ba0c31893..3249be45c40 100644
--- a/benchmarks/FfiBoringssl/dart/FfiBoringssl.dart
+++ b/benchmarks/FfiBoringssl/dart/FfiBoringssl.dart
@@ -27,7 +27,7 @@ Uint8List inventData(int length) {
   return result;
 }
 
-Uint8List toUint8List(Bytes bytes, int length) {
+Uint8List toUint8List(Pointer<Bytes> bytes, int length) {
   final result = Uint8List(length);
   final uint8bytes = bytes.asUint8Pointer();
   for (int i = 0; i < length; i++) {
@@ -36,7 +36,7 @@ Uint8List toUint8List(Bytes bytes, int length) {
   return result;
 }
 
-void copyFromUint8ListToTarget(Uint8List source, Data target) {
+void copyFromUint8ListToTarget(Uint8List source, Pointer<Data> target) {
   final int length = source.length;
   final uint8target = target.asUint8Pointer();
   for (int i = 0; i < length; i++) {
@@ -52,7 +52,7 @@ String hash(Pointer<Data> data, int length, Pointer<EVP_MD> hashAlgorithm) {
   final Pointer<Bytes> result = calloc<Uint8>(resultSize).cast();
   EVP_DigestFinal(context, result, nullptr);
   EVP_MD_CTX_free(context);
-  final String hash = base64Encode(toUint8List(result.ref, resultSize));
+  final String hash = base64Encode(toUint8List(result, resultSize));
   calloc.free(result);
   return hash;
 }
@@ -85,7 +85,7 @@ class DigestCMemory extends BenchmarkBase {
   @override
   void setup() {
     data = calloc<Uint8>(L).cast();
-    copyFromUint8ListToTarget(inventData(L), data.ref);
+    copyFromUint8ListToTarget(inventData(L), data);
     hash(data, L, hashAlgorithm);
   }
 
@@ -115,7 +115,7 @@ class DigestDartMemory extends BenchmarkBase {
   void setup() {
     data = inventData(L);
     final Pointer<Data> dataInC = calloc<Uint8>(L).cast();
-    copyFromUint8ListToTarget(data, dataInC.ref);
+    copyFromUint8ListToTarget(data, dataInC);
     hash(dataInC, L, hashAlgorithm);
     calloc.free(dataInC);
   }
@@ -126,7 +126,7 @@ class DigestDartMemory extends BenchmarkBase {
   @override
   void run() {
     final Pointer<Data> dataInC = calloc<Uint8>(L).cast();
-    copyFromUint8ListToTarget(data, dataInC.ref);
+    copyFromUint8ListToTarget(data, dataInC);
     final String result = hash(dataInC, L, hashAlgorithm);
     calloc.free(dataInC);
     if (result != expectedHash) {
diff --git a/benchmarks/FfiBoringssl/dart/types.dart b/benchmarks/FfiBoringssl/dart/types.dart
index 2dd5f76ae42..972555e105e 100644
--- a/benchmarks/FfiBoringssl/dart/types.dart
+++ b/benchmarks/FfiBoringssl/dart/types.dart
@@ -7,21 +7,25 @@
 import 'dart:ffi';
 
 /// digest algorithm.
-class EVP_MD extends Struct {}
+class EVP_MD extends Opaque {}
 
 /// digest context.
-class EVP_MD_CTX extends Struct {}
+class EVP_MD_CTX extends Opaque {}
 
 /// Type for `void*` used to represent opaque data.
-class Data extends Struct {
-  static Data fromUint8Pointer(Pointer<Uint8> p) => p.cast<Data>().ref;
+class Data extends Opaque {
+  static Pointer<Data> fromUint8Pointer(Pointer<Uint8> p) => p.cast<Data>();
+}
 
-  Pointer<Uint8> asUint8Pointer() => addressOf.cast();
+extension DataPointerAsUint8Pointer on Pointer<Data> {
+  Pointer<Uint8> asUint8Pointer() => cast();
 }
 
 /// Type for `uint8_t*` used to represent byte data.
-class Bytes extends Struct {
-  static Data fromUint8Pointer(Pointer<Uint8> p) => p.cast<Data>().ref;
-
-  Pointer<Uint8> asUint8Pointer() => addressOf.cast();
+class Bytes extends Opaque {
+  static Pointer<Data> fromUint8Pointer(Pointer<Uint8> p) => p.cast<Data>();
+}
+
+extension BytesPointerAsUint8Pointer on Pointer<Bytes> {
+  Pointer<Uint8> asUint8Pointer() => cast();
 }
diff --git a/benchmarks/FfiBoringssl/dart2/FfiBoringssl.dart b/benchmarks/FfiBoringssl/dart2/FfiBoringssl.dart
index 6bd064aa3c6..c749745d740 100644
--- a/benchmarks/FfiBoringssl/dart2/FfiBoringssl.dart
+++ b/benchmarks/FfiBoringssl/dart2/FfiBoringssl.dart
@@ -29,7 +29,7 @@ Uint8List inventData(int length) {
   return result;
 }
 
-Uint8List toUint8List(Bytes bytes, int length) {
+Uint8List toUint8List(Pointer<Bytes> bytes, int length) {
   final result = Uint8List(length);
   final uint8bytes = bytes.asUint8Pointer();
   for (int i = 0; i < length; i++) {
@@ -38,7 +38,7 @@ Uint8List toUint8List(Bytes bytes, int length) {
   return result;
 }
 
-void copyFromUint8ListToTarget(Uint8List source, Data target) {
+void copyFromUint8ListToTarget(Uint8List source, Pointer<Data> target) {
   final int length = source.length;
   final uint8target = target.asUint8Pointer();
   for (int i = 0; i < length; i++) {
@@ -54,7 +54,7 @@ String hash(Pointer<Data> data, int length, Pointer<EVP_MD> hashAlgorithm) {
   final Pointer<Bytes> result = calloc<Uint8>(resultSize).cast();
   EVP_DigestFinal(context, result, nullptr);
   EVP_MD_CTX_free(context);
-  final String hash = base64Encode(toUint8List(result.ref, resultSize));
+  final String hash = base64Encode(toUint8List(result, resultSize));
   calloc.free(result);
   return hash;
 }
@@ -87,7 +87,7 @@ class DigestCMemory extends BenchmarkBase {
   @override
   void setup() {
     data = calloc<Uint8>(L).cast();
-    copyFromUint8ListToTarget(inventData(L), data.ref);
+    copyFromUint8ListToTarget(inventData(L), data);
     hash(data, L, hashAlgorithm);
   }
 
@@ -117,7 +117,7 @@ class DigestDartMemory extends BenchmarkBase {
   void setup() {
     data = inventData(L);
     final Pointer<Data> dataInC = calloc<Uint8>(L).cast();
-    copyFromUint8ListToTarget(data, dataInC.ref);
+    copyFromUint8ListToTarget(data, dataInC);
     hash(dataInC, L, hashAlgorithm);
     calloc.free(dataInC);
   }
@@ -128,7 +128,7 @@ class DigestDartMemory extends BenchmarkBase {
   @override
   void run() {
     final Pointer<Data> dataInC = calloc<Uint8>(L).cast();
-    copyFromUint8ListToTarget(data, dataInC.ref);
+    copyFromUint8ListToTarget(data, dataInC);
     final String result = hash(dataInC, L, hashAlgorithm);
     calloc.free(dataInC);
     if (result != expectedHash) {
diff --git a/benchmarks/FfiBoringssl/dart2/types.dart b/benchmarks/FfiBoringssl/dart2/types.dart
index 2c1923ba682..5ceb6a95c00 100644
--- a/benchmarks/FfiBoringssl/dart2/types.dart
+++ b/benchmarks/FfiBoringssl/dart2/types.dart
@@ -9,21 +9,25 @@
 import 'dart:ffi';
 
 /// digest algorithm.
-class EVP_MD extends Struct {}
+class EVP_MD extends Opaque {}
 
 /// digest context.
-class EVP_MD_CTX extends Struct {}
+class EVP_MD_CTX extends Opaque {}
 
 /// Type for `void*` used to represent opaque data.
-class Data extends Struct {
-  static Data fromUint8Pointer(Pointer<Uint8> p) => p.cast<Data>().ref;
+class Data extends Opaque {
+  static Pointer<Data> fromUint8Pointer(Pointer<Uint8> p) => p.cast<Data>();
+}
 
-  Pointer<Uint8> asUint8Pointer() => addressOf.cast();
+extension DataPointerAsUint8Pointer on Pointer<Data> {
+  Pointer<Uint8> asUint8Pointer() => cast();
 }
 
 /// Type for `uint8_t*` used to represent byte data.
-class Bytes extends Struct {
-  static Data fromUint8Pointer(Pointer<Uint8> p) => p.cast<Data>().ref;
-
-  Pointer<Uint8> asUint8Pointer() => addressOf.cast();
+class Bytes extends Opaque {
+  static Pointer<Data> fromUint8Pointer(Pointer<Uint8> p) => p.cast<Data>();
+}
+
+extension BytesPointerAsUint8Pointer on Pointer<Bytes> {
+  Pointer<Uint8> asUint8Pointer() => cast();
 }
diff --git a/runtime/tests/vm/dart/isolates/dart_api_create_lightweight_isolate_test.dart b/runtime/tests/vm/dart/isolates/dart_api_create_lightweight_isolate_test.dart
index 25e0199eb00..ecc33a10d64 100644
--- a/runtime/tests/vm/dart/isolates/dart_api_create_lightweight_isolate_test.dart
+++ b/runtime/tests/vm/dart/isolates/dart_api_create_lightweight_isolate_test.dart
@@ -22,7 +22,7 @@ final bool isolateGropusEnabled =
     Platform.executableArguments.contains('--enable-isolate-groups');
 final sdkRoot = Platform.script.resolve('../../../../../');
 
-class Isolate extends Struct {}
+class Isolate extends Opaque {}
 
 abstract class FfiBindings {
   static final ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");
diff --git a/runtime/tests/vm/dart/isolates/thread_pool_test.dart b/runtime/tests/vm/dart/isolates/thread_pool_test.dart
index 7a301bc0952..3d689ca4254 100644
--- a/runtime/tests/vm/dart/isolates/thread_pool_test.dart
+++ b/runtime/tests/vm/dart/isolates/thread_pool_test.dart
@@ -16,7 +16,7 @@ import '../../../../../tests/ffi/dylib_utils.dart';
 // This should be larger than max-new-space-size/tlab-size.
 const int threadCount = 200;
 
-class Isolate extends Struct {}
+class Isolate extends Opaque {}
 
 typedef Dart_CurrentIsolateFT = Pointer<Isolate> Function();
 typedef Dart_CurrentIsolateNFT = Pointer<Isolate> Function();
diff --git a/runtime/tests/vm/dart_2/isolates/dart_api_create_lightweight_isolate_test.dart b/runtime/tests/vm/dart_2/isolates/dart_api_create_lightweight_isolate_test.dart
index d35474e27f2..bcd62700f2b 100644
--- a/runtime/tests/vm/dart_2/isolates/dart_api_create_lightweight_isolate_test.dart
+++ b/runtime/tests/vm/dart_2/isolates/dart_api_create_lightweight_isolate_test.dart
@@ -22,7 +22,7 @@ final bool isolateGropusEnabled =
     Platform.executableArguments.contains('--enable-isolate-groups');
 final sdkRoot = Platform.script.resolve('../../../../../');
 
-class Isolate extends Struct {}
+class Isolate extends Opaque {}
 
 abstract class FfiBindings {
   static final ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");
diff --git a/runtime/tests/vm/dart_2/isolates/thread_pool_test.dart b/runtime/tests/vm/dart_2/isolates/thread_pool_test.dart
index ff8a7e69448..695fda23735 100644
--- a/runtime/tests/vm/dart_2/isolates/thread_pool_test.dart
+++ b/runtime/tests/vm/dart_2/isolates/thread_pool_test.dart
@@ -16,7 +16,7 @@ import '../../../../../tests/ffi_2/dylib_utils.dart';
 // This should be larger than max-new-space-size/tlab-size.
 const int threadCount = 200;
 
-class Isolate extends Struct {}
+class Isolate extends Opaque {}
 
 typedef Dart_CurrentIsolateFT = Pointer<Isolate> Function();
 typedef Dart_CurrentIsolateNFT = Pointer<Isolate> Function();
diff --git a/samples/ffi/sqlite/lib/src/database.dart b/samples/ffi/sqlite/lib/src/database.dart
index 59da929162b..5031027f79f 100644
--- a/samples/ffi/sqlite/lib/src/database.dart
+++ b/samples/ffi/sqlite/lib/src/database.dart
@@ -101,7 +101,7 @@ class Database {
     int columnCount = bindings.sqlite3_column_count(statement);
     for (int i = 0; i < columnCount; i++) {
       String columnName =
-          bindings.sqlite3_column_name(statement, i).ref.toString();
+          Utf8.fromUtf8(bindings.sqlite3_column_name(statement, i));
       columnIndices[columnName] = i;
     }
 
@@ -109,9 +109,9 @@ class Database {
   }
 
   SQLiteException _loadError(int errorCode) {
-    String errorMessage = bindings.sqlite3_errmsg(_database).ref.toString();
+    String errorMessage = Utf8.fromUtf8(bindings.sqlite3_errmsg(_database));
     String errorCodeExplanation =
-        bindings.sqlite3_errstr(errorCode).ref.toString();
+        Utf8.fromUtf8(bindings.sqlite3_errstr(errorCode));
     return SQLiteException(
         "$errorMessage (Code $errorCode: $errorCodeExplanation)");
   }
@@ -206,10 +206,8 @@ class Row {
       dynamicType =
           _typeFromCode(bindings.sqlite3_column_type(_statement, columnIndex));
     } else {
-      dynamicType = _typeFromText(bindings
-          .sqlite3_column_decltype(_statement, columnIndex)
-          .ref
-          .toString());
+      dynamicType = _typeFromText(Utf8.fromUtf8(
+          bindings.sqlite3_column_decltype(_statement, columnIndex)));
     }
 
     switch (dynamicType) {
@@ -244,7 +242,7 @@ class Row {
   /// Reads column [columnIndex] and converts to [Type.Text] if not text.
   String readColumnByIndexAsText(int columnIndex) {
     _checkIsCurrentRow();
-    return bindings.sqlite3_column_text(_statement, columnIndex).ref.toString();
+    return Utf8.fromUtf8(bindings.sqlite3_column_text(_statement, columnIndex));
   }
 
   void _checkIsCurrentRow() {
diff --git a/samples/ffi/sqlite/test/sqlite_test.dart b/samples/ffi/sqlite/test/sqlite_test.dart
index fedc9e55659..ef7666d289b 100644
--- a/samples/ffi/sqlite/test/sqlite_test.dart
+++ b/samples/ffi/sqlite/test/sqlite_test.dart
@@ -167,7 +167,7 @@ void main() {
   test("Utf8 unit test", () {
     final String test = 'Hasta Mañana';
     final medium = Utf8.toUtf8(test);
-    expect(test, medium.ref.toString());
+    expect(test, Utf8.fromUtf8(medium));
     calloc.free(medium);
   });
 }
diff --git a/samples_2/ffi/sqlite/lib/src/database.dart b/samples_2/ffi/sqlite/lib/src/database.dart
index 49f229f4232..687fea87e99 100644
--- a/samples_2/ffi/sqlite/lib/src/database.dart
+++ b/samples_2/ffi/sqlite/lib/src/database.dart
@@ -103,7 +103,7 @@ class Database {
     int columnCount = bindings.sqlite3_column_count(statement);
     for (int i = 0; i < columnCount; i++) {
       String columnName =
-          bindings.sqlite3_column_name(statement, i).ref.toString();
+          Utf8.fromUtf8(bindings.sqlite3_column_name(statement, i));
       columnIndices[columnName] = i;
     }
 
@@ -111,12 +111,12 @@ class Database {
   }
 
   SQLiteException _loadError([int errorCode]) {
-    String errorMessage = bindings.sqlite3_errmsg(_database).ref.toString();
+    String errorMessage = Utf8.fromUtf8(bindings.sqlite3_errmsg(_database));
     if (errorCode == null) {
       return SQLiteException(errorMessage);
     }
     String errorCodeExplanation =
-        bindings.sqlite3_errstr(errorCode).ref.toString();
+        Utf8.fromUtf8(bindings.sqlite3_errstr(errorCode));
     return SQLiteException(
         "$errorMessage (Code $errorCode: $errorCodeExplanation)");
   }
@@ -216,10 +216,8 @@ class Row {
       dynamicType =
           _typeFromCode(bindings.sqlite3_column_type(_statement, columnIndex));
     } else {
-      dynamicType = _typeFromText(bindings
-          .sqlite3_column_decltype(_statement, columnIndex)
-          .ref
-          .toString());
+      dynamicType = _typeFromText(Utf8.fromUtf8(
+          bindings.sqlite3_column_decltype(_statement, columnIndex)));
     }
 
     switch (dynamicType) {
@@ -255,7 +253,7 @@ class Row {
   /// Reads column [columnIndex] and converts to [Type.Text] if not text.
   String readColumnByIndexAsText(int columnIndex) {
     _checkIsCurrentRow();
-    return bindings.sqlite3_column_text(_statement, columnIndex).ref.toString();
+    return Utf8.fromUtf8(bindings.sqlite3_column_text(_statement, columnIndex));
   }
 
   void _checkIsCurrentRow() {
diff --git a/samples_2/ffi/sqlite/test/sqlite_test.dart b/samples_2/ffi/sqlite/test/sqlite_test.dart
index f27336bd22a..dffbe5bb9e6 100644
--- a/samples_2/ffi/sqlite/test/sqlite_test.dart
+++ b/samples_2/ffi/sqlite/test/sqlite_test.dart
@@ -171,7 +171,7 @@ void main() {
   test("Utf8 unit test", () {
     final String test = 'Hasta Mañana';
     final medium = Utf8.toUtf8(test);
-    expect(test, medium.ref.toString());
+    expect(test, Utf8.fromUtf8(medium));
     calloc.free(medium);
   });
 }
diff --git a/tests/ffi/vmspecific_regress_37100_test.dart b/tests/ffi/vmspecific_regress_37100_test.dart
index a819503c12a..ef4c6149d72 100644
--- a/tests/ffi/vmspecific_regress_37100_test.dart
+++ b/tests/ffi/vmspecific_regress_37100_test.dart
@@ -10,7 +10,7 @@ import "package:expect/expect.dart";
 
 import 'dylib_utils.dart';
 
-class EVP_MD extends Struct {}
+class EVP_MD extends Opaque {}
 
 DynamicLibrary ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");
 
diff --git a/tests/ffi_2/vmspecific_regress_37100_test.dart b/tests/ffi_2/vmspecific_regress_37100_test.dart
index a819503c12a..ef4c6149d72 100644
--- a/tests/ffi_2/vmspecific_regress_37100_test.dart
+++ b/tests/ffi_2/vmspecific_regress_37100_test.dart
@@ -10,7 +10,7 @@ import "package:expect/expect.dart";
 
 import 'dylib_utils.dart';
 
-class EVP_MD extends Struct {}
+class EVP_MD extends Opaque {}
 
 DynamicLibrary ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");