The magician opens a red box and reveals a black box inside. Inside the black box he takes out a red sponge ball. Now the red box is closed and placed inside the black box. 

The boxes are opened again. A blue sponge ball appears inside the box. The process is repeated again and a yellow sponge ball appears when the boxes are opened. 

No manipulation required. 
Size: 4.4cm x 4cm x 3.5cm