diff --git a/lib/button_stagger_animation.dart b/lib/button_stagger_animation.dart
index 57ba1a7..fcf6005 100644
--- a/lib/button_stagger_animation.dart
+++ b/lib/button_stagger_animation.dart
@@ -10,19 +10,23 @@ class ButtonStaggerAnimation extends StatelessWidget {
   final double progressIndicatorSize;
   final BorderRadius borderRadius;
   final double strokeWidth;
-  final Function(AnimationController) onPressed;
+  final Function(AnimationController)? onPressed;
   final Widget child;
+  final bool outlined;
+  final double height;
 
   ButtonStaggerAnimation({
-    Key key,
-    this.controller,
-    this.color,
-    this.progressIndicatorColor,
-    this.progressIndicatorSize,
-    this.borderRadius,
-    this.onPressed,
-    this.strokeWidth,
-    this.child,
+    Key? key,
+    required this.controller,
+    required this.color,
+    required this.progressIndicatorColor,
+    required this.progressIndicatorSize,
+    required this.borderRadius,
+    required this.onPressed,
+    required this.strokeWidth,
+    required this.child,
+    required this.outlined,
+    required this.height,
   }) : super(key: key);
 
   @override
@@ -50,7 +54,7 @@ class ButtonStaggerAnimation extends StatelessWidget {
       BuildContext context, BoxConstraints constraints) {
     var buttonHeight = (constraints.maxHeight != double.infinity)
         ? constraints.maxHeight
-        : 60.0;
+        : height;
 
     var widthAnimation = Tween<double>(
       begin: constraints.maxWidth,
@@ -76,16 +80,35 @@ class ButtonStaggerAnimation extends StatelessWidget {
         return SizedBox(
           height: buttonHeight,
           width: widthAnimation.value,
-          child: RaisedButton(
-            shape: RoundedRectangleBorder(
-              borderRadius: borderRadiusAnimation.value,
-            ),
-            color: color,
-            child: _buttonChild(),
-            onPressed: () {
-              this.onPressed(controller);
-            },
-          ),
+          child: outlined
+              ? OutlinedButton(
+                  style: OutlinedButton.styleFrom(
+                    primary: color,
+                    shape: RoundedRectangleBorder(
+                      borderRadius: borderRadiusAnimation.value,
+                    ),
+                  ),
+                  onPressed: onPressed != null
+                      ? () {
+                          onPressed!(controller);
+                        }
+                      : null,
+                  child: _buttonChild(),
+                )
+              : ElevatedButton(
+                  style: ElevatedButton.styleFrom(
+                    primary: color,
+                    shape: RoundedRectangleBorder(
+                      borderRadius: borderRadiusAnimation.value,
+                    ),
+                  ),
+                  onPressed: onPressed != null
+                      ? () {
+                          onPressed!(controller);
+                        }
+                      : null,
+                  child: _buttonChild(),
+                ),
         );
       },
     );
diff --git a/lib/progress_button.dart b/lib/progress_button.dart
index 7039236..a6683c7 100644
--- a/lib/progress_button.dart
+++ b/lib/progress_button.dart
@@ -6,34 +6,49 @@ import 'package:progress_indicator_button/button_stagger_animation.dart';
 class ProgressButton extends StatefulWidget {
   /// The background color of the button.
   final Color color;
+
   /// The progress indicator color.
   final Color progressIndicatorColor;
+
   /// The size of the progress indicator.
   final double progressIndicatorSize;
+
   /// The border radius while NOT animating.
   final BorderRadius borderRadius;
+
   /// The duration of the animation.
   final Duration animationDuration;
 
   /// The stroke width of progress indicator.
   final double strokeWidth;
+
+  /// Changes to an outlined button.
+  final bool outlined;
+
+  /// The height of the button unless it is constrained.
+  final double height;
+
   /// Function that will be called at the on pressed event.
   ///
   /// This will grant access to its [AnimationController] so
   /// that the animation can be controlled based on the need.
-  final Function(AnimationController) onPressed;
+  /// If it is null, the button will be disabled.
+  final Function(AnimationController)? onPressed;
+
   /// The child to display on the button.
   final Widget child;
 
   ProgressButton({
-    @required this.child,
-    @required this.onPressed,
+    required this.child,
+    required this.onPressed,
     this.color = Colors.blue,
     this.strokeWidth = 2,
     this.progressIndicatorColor = Colors.white,
     this.progressIndicatorSize = 30,
     this.borderRadius = const BorderRadius.all(Radius.circular(0)),
     this.animationDuration = const Duration(milliseconds: 300),
+    this.outlined = false,
+    this.height = 60.0,
   });
 
   @override
@@ -42,7 +57,7 @@ class ProgressButton extends StatefulWidget {
 
 class _ProgressButtonState extends State<ProgressButton>
     with TickerProviderStateMixin {
-  AnimationController _controller;
+  AnimationController? _controller;
 
   @override
   void initState() {
@@ -56,7 +71,7 @@ class _ProgressButtonState extends State<ProgressButton>
 
   @override
   void dispose() {
-    _controller.dispose();
+    _controller?.dispose();
     super.dispose();
   }
 
@@ -64,13 +79,15 @@ class _ProgressButtonState extends State<ProgressButton>
   Widget build(BuildContext context) {
     return Center(
       child: ButtonStaggerAnimation(
-        controller: _controller.view,
+        controller: _controller!,
         color: widget.color,
         strokeWidth: widget.strokeWidth,
         progressIndicatorColor: widget.progressIndicatorColor,
         progressIndicatorSize: widget.progressIndicatorSize,
         borderRadius: widget.borderRadius,
         onPressed: widget.onPressed,
+        outlined: widget.outlined,
+        height: widget.height,
         child: widget.child,
       ),
     );
diff --git a/pubspec.yaml b/pubspec.yaml
index cbc0389..367508d 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,11 +1,11 @@
 name: progress_indicator_button
 description: A simple button which can transform and show a progress indicator.
-version: 0.0.3
+version: 0.0.4
 author: Pascal Brosinski<pascal@brosinski.eu>
 homepage: https://github.com/PascalAC/progress_button
 
 environment:
-  sdk: ">=2.0.0-dev.68.0 <3.0.0"
+  sdk: ">=2.12.0 <3.0.0"
 
 dependencies:
   flutter:
diff --git a/test/progress_button_test.dart b/test/progress_button_test.dart
index 036913f..f60eba4 100644
--- a/test/progress_button_test.dart
+++ b/test/progress_button_test.dart
@@ -5,14 +5,16 @@ import 'package:progress_indicator_button/progress_button.dart';
 import '../example/lib/src/app.dart';
 
 void main() {
-  testWidgets('ProgressButton - Start animation on click', (WidgetTester tester) async {
+  testWidgets('ProgressButton - Start animation on click',
+      (WidgetTester tester) async {
     await tester.pumpWidget(App());
 
     expect(find.byType(ProgressButton), findsOneWidget);
 
-    await tester.tap(find.byType(RaisedButton));
+    await tester.tap(find.byType(ElevatedButton));
 
-    final widget = tester.widget<ButtonStaggerAnimation>(find.byType(ButtonStaggerAnimation));
+    final widget = tester
+        .widget<ButtonStaggerAnimation>(find.byType(ButtonStaggerAnimation));
     expect(widget.controller.isAnimating, true);
   });
 }