yes they are right side left side specific,the lower holes are set up in an angle not perpendicular to the ball joint centerline which would put the lower ball joint in an inproper angle thus affecting bumpsteer,header clearance and who knows what else but heres some pic's of 10" drum setup,kelsey hayes four piston setup and big bolt setup the pics are of drivers side on all three setups for comparison,not trying to diss anyone but these are the fact's .................Wagg's pay close attention to the ball joint centerline then draw a line thru the lower ball joint mounting bolt centerline. The big bolt pattern discs are NOT side specific
