Remember Jim, that is a rocker flex binding. I cant remember if the brake is different from the PX race (which as Phil says is also different from the regular PX). I have a few pairs of these sitting so will double check
BTW, these are terrific deals for Rockerflex bindings. For anyone looking to mount these on a Rossi plate, they only work on the R21 plate. While you can actually mount the previous PX race/MFX binding (for the R20 plate) on the R21 plate you cant easily mount the RF on the older R20 Plate. Alo, if anyone is planning to mount these flat i.e not on a Rossi plate) be prepared to shim the toe a lot (~5mm) as the Rockerflex heel sits high and will give a lot of ramp/delta. on the R21 plate the rear plate is normally (4mm?) thinner to compensate for this. (mounting the older binding on the R21 plate gives a nice gas pedal!)
Updated. Yes the 15 Rockerflex brake is the same as the PX Race/MFX brake. Picture below shows the RF/PX race brake on the right v. regular (at least I think so, this was in my box of brakes!) PX brake. Looks very similar above but different fitting underneath