diff --git a/Engine.Physics2D/PhysicsMaterial2D.cs b/Engine.Physics2D/PhysicsMaterial2D.cs
index a3875ca..bb48c82 100644
--- a/Engine.Physics2D/PhysicsMaterial2D.cs
+++ b/Engine.Physics2D/PhysicsMaterial2D.cs
@@ -1,7 +1,7 @@
 namespace Engine.Physics2D;
 
-public readonly struct PhysicsMaterial2D(float Friction, float Restitution) : IPhysicsMaterial2D
+public class PhysicsMaterial2D(float Friction, float Restitution) : IPhysicsMaterial2D
 {
-    public readonly float Friction { get; init; } = Friction;
-    public readonly float Restitution { get; init; } = Restitution;
+    public float Friction { get; set; } = Friction;
+    public float Restitution { get; set; } = Restitution;
 }
diff --git a/Engine.Physics2D/PhysicsMaterial2DDefault.cs b/Engine.Physics2D/PhysicsMaterial2DDefault.cs
deleted file mode 100644
index 1ed446e..0000000
--- a/Engine.Physics2D/PhysicsMaterial2DDefault.cs
+++ /dev/null
@@ -1,8 +0,0 @@
-namespace Engine.Physics2D;
-
-public readonly struct PhysicsMaterial2DDefault : IPhysicsMaterial2D
-{
-    public readonly float Friction => .1f;
-
-    public readonly float Restitution => .1f;
-}
diff --git a/Engine.Physics2D/ReadOnlyPhysicsMaterial2D.cs b/Engine.Physics2D/ReadOnlyPhysicsMaterial2D.cs
new file mode 100644
index 0000000..fe3f79c
--- /dev/null
+++ b/Engine.Physics2D/ReadOnlyPhysicsMaterial2D.cs
@@ -0,0 +1,9 @@
+namespace Engine.Physics2D;
+
+public readonly struct ReadOnlyPhysicsMaterial2D(float Friction, float Restitution) : IPhysicsMaterial2D
+{
+    public readonly float Friction { get; } = Friction;
+    public readonly float Restitution { get; } = Restitution;
+
+    public readonly static ReadOnlyPhysicsMaterial2D Default = new(.1f, .1f);
+}
diff --git a/Engine.Physics2D/RigidBody2D.cs b/Engine.Physics2D/RigidBody2D.cs
index 3c5a96e..dbf97be 100644
--- a/Engine.Physics2D/RigidBody2D.cs
+++ b/Engine.Physics2D/RigidBody2D.cs
@@ -6,7 +6,7 @@ public class RigidBody2D : Behaviour2D, IRigidBody2D
 {
     private const float LOWEST_ALLOWED_MASS = 0.00001f;
 
-    public IPhysicsMaterial2D Material { get; set; } = new PhysicsMaterial2DDefault();
+    public IPhysicsMaterial2D Material { get; set; } = ReadOnlyPhysicsMaterial2D.Default;
 
     public Vector2D Velocity { get; set; } = Vector2D.Zero;
     public float AngularVelocity { get; set; } = 0f;