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
The HD2 tracked platform is a large, heavy duty tracked robot with the power to pull a truck and climb stairs. A wealth of internal space allows for batteries, controls and an optional computer. Customized version of item TP-200-001.
Waterproof ultrasonic distance sensor. This sensor can be used for collision detection in your project.