4

4 is the set number for five LEGO sets. It could refer to any one of the following:
4 Large House Set.jpg|4 Large House Set
4 Basic Set.jpg|4 Basic Set
4-Propellers and Wheels.gif|4 Propellers & Wheels
4 Velveeta Promotional Set No 4.png|4 Velveeta Promotional Set No 4
4-4.5V Motor Battery Cables.jpg|4 4.5V Motor Battery Cables