Park tool hydraulic brake piston press pp1 2the unique wedge shaped pp 1 slides into a hydraulic disc brake caliper to pre set the piston when replacing pads aligning pads and performing other service procedures makes hydraulic disc brake maintenance and repair faster and easier the park tool pp 1 slides between the brake pads inside a caliper allowing the user to spread the pads and compress the pistons when servicing pads or wheels the pp 1 expands the gap between the pads making it easy