RP Rear Hub Adapters for the BRP Tires.
These hubs will Fit 
HPI Baja Rear , Losi 5 Front and Rear, MCD Front and Rear, Kraken Vekta.5 Front and Rear
These are the Rear hub adapters for your HPI Baja that allow the use the World Famous BRP (Bishop Racing Products) 1/4 scale tires and wheels.
These adapters are machined out of  6061 aluminum and are sold as a pair. (2 hubs)
The rear hubs are pre-drilled for the stock 4mm pin and the 5mm pin.
They also have an Oil and Chemical Resistant O-ring that is designed as an additional safety backup to keep your stub axle pins in place.
They come pre-assembled with hardened wheel studs and stainless nyloc nuts .