You need to take the spindle in if you don't know what model number. Probably a UFP, in which case it's easy. Also, if you're even in a spot where you need to rebuild it -- remember a whole new preassembled trailing arm/spindle, bearings, hub, rotor, caliper and pads only costs $200-220. One bolt to the axle and one bolt to the brake line and you have a new setup.