Park Tool PP 1.2 Hydraulic Brake Piston Press. Make hydraulic disc brake maintenance and repair faster and easier with a Park Tool Hydraulic Piston Press. The unique, wedge shaped tool slides into a hydraulic disc brake caliper to pre set the piston when replacing pads, aligning pads, and performing other service procedures. The Park Tool PP 1.2 slides between the brake pads inside a caliper allowing you to spread the pads and compress the pistons when servicing pads or wheels. The PP 1.2 expands the gap between the pads, making it easy to insert the disc between the pads when reinstalling a caliper or wheel.