W420 Steel Ball Universal Wheel Good for 2WD Car Chasse can be used at the back of the 2wd Robot so the robot can move freely with 2 wheels.  

Specifications:

• Steel ball size and material: Φ 15
• Scaffold material: nylon
• Fixed frame pitch: 40 mm
• Fixed hole diameter: 3.1 mm Φ
• Universal wheel overall height: 20 mm
• Bearing: the bearing is less than 100 g is recommended.
  
  Shipping list:

1 x W420 steel ball universal wheel.