This is a robot drive wheel we had made specifically for us. It does not have a bearing. Its 6 inches in diameter. 1.9" inches wide. Its a rubber pneumatic tube tire. The rim has a 4 bolt pattern so you can easily mount it to a flanged hub.
This is a MLT-JR tracked robot platform and is equipped with 32mm motors, a motor controller, and Spektrum remote control. This robot is a prebuilt version of TP-220-001, and can handle up to 8lbs of additional payload/speeds up to 300 feet per minute.