Metal caster wheel 30mm, is 1mm thick steel plate stamping on the machine, load 50KG no problem, and exquisite workmanship, this caster strong and lightweight, 30mm height wheel body, with a total weight of only 120gm. And there are many big ball around 120 small ball around, rotate the main scroll ball smoother. This allows the robot to walk or move to a more flexible and comfortable, and the other parameters are as follows: * Mounting holes: 5mm * Mounting holes center distance: 55mm * Round total body height: 30mm * Bovine Ball diameter: 24mm * Bull's-eye ball protruding height: 9mm * Slide the small ball number: 120 Wheels Total weight: 120g * Maximum load: 50KG