This is a used caliper off of the King Motorsports/Mugen World Challenge RSX. Also equivalent to calipers used in earlier NASCAR applications. The other caliper was badly damaged so it is just the one. Buy for a spare or to complete a set, or just for nostalgia! 

Radial mount Alcon B-Type, forged two piece caliper. Nitride coated Pistons with anti-knock back springs. 

Specs:

Suits 12-13" rotors, 28-32mm widths

Pistons: 1-7/8 (48mm), 1-3/4 (44mm)

Mounting: 6" (152mm) post to post