There are two types of sliding calipers, the LD sliding caliper unit is operated by one piston per caliper. The caliper and steering arm are cast as one piece and combined with the spindle stem to form an integral spindle assembly.
The light duty system is used on all F-150 and Bronco models.
The HD slider caliper unit contains 2 pistons on the same side of the rotor. The caliper slides on the support assembly and is retained by a key and spring.
The heavy duty system is used on all F-250, F-350 and F-Super Duty models.