Image Item No. Description By  4180c01 (Inv)  Brick, Modified 2 x 4 with Black Wheels, Train Spoked Small (23mm D.) and Black Pins (4180 / wheel3 / 2344) Catalog: Parts: Wheel 3  4180c05 (Inv)  Brick, Modified 2 x 4 with Red Wheels, Train Spoked Large (29mm D.) and Red Pins (4180 / wheel4 / 2344) Catalog: Parts: Wheel 4  4185  Technic Wedge Belt Wheel (Pulley) Catalog: Parts: Wheel 39790