This is a pair of Replacement Tires and Wheels for the Tamiya RC serries.  We use the on our mini ATR Robot Kits. 

Usually tires like this are two parts and you end up buying the Rims and the Tires for a lot more than these cost already assembled.  These are one-piece chrome plated plastic wheels. Offset V-tread rubber tires. Tires are pre-mounted and glued to the rims.

The tires are ~4" in diameter and ~2 5/8" in width. The wheel's inner hub have a 12mm hex drive.   The wheels are off-set 7/8" from the inside edge of the rim to outside edge of the drive washer.