The brake caliper is a component that applies force to the brake disc. The hydraulic pressure generated by the brake master cylinder ultimately acts on the piston inside the caliper, which expands and pushes the brake pads towards the brake disc.
Handbrake calipers, is also known as parking brake calipers. It is commonly used for braking when the vehicles are parked. 
The structure of these calipers are more complicated than those calipers for front axles. 
They are mainly consist of the caliper body, internal handbrake mechanism unit and some hardware on top of the products.
To insure the quality and performance of these calipers, we have parking brake function test, high/low temperature seal test and piston returning test etc.