Sim Racing Castor Pad

I recently treated my self to a sim racing wheel and pedals. I quickly found that my office chairs castors made it impossible to play the game without rolling around. I designed these little things based on my home chair. I put one on each wheel and they hold my seat in place nicely!

Not sure if castors are a common size, but they fit both my seats at home well. I've included the FreeCad files if anyone needs to resize.