This is a 9V battery clip typically used for our wireless cameras. The ID is 2.1mm, the OD is 5.5mm. Center positive.
9V Battery Snap with 12" Leads
This is powerful wheelchair motor. They make great heavy-duty robot motors. 250W 75RPM motors with 17mm keyed shaft output. They are sold individually and have an electric brake mounted on the back.
This is an Enclosed 6-wheel drive robot. Ideally suited for Autonomous Robot Development! It uses six powerful wheelchair motors and the inside robot cavity has plenty of room for electronics.