Brake shoes contain asbestos, which has been determined to be a cancer causing agent. Never clean the brake surfaces with compressed air! Avoid inhaling any dust from any brake surface! When cleaning brake surfaces, use a commercially available brake cleaning fluid.
There are two types of sliding calipers, the LD sliding caliper unit is operated by one piston per caliper.
The HD slider caliper unit contains two pistons on the same side of the rotor. The caliper slides on the support assembly and is retained by a key and spring.