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
Indoor GPS Starter Kit featuring one Modem and five Beacons to get your project running. Accurately position your robot to a couple centimeters indoors! Indoor Positioning System (IPS)
This is a MLT-42-F tracked robot platform and is equipped with flipper arms, 42mm motors, a motor controller, and Spektrum remote control. This rugged robot platform the treaded robot handles up to 15lbs of additional payload and travels 200ft/min.