A single set of OE equivalent pistons and seals for a front 4 pot Brembo STI caliper for Impreza WRX STI 2001-2018.
Comes with all items shown in the image, which includes 8 pistons and associated seals and rings and bleed screws. This kit contains what you need for one caliper, aside from brake fluid.
2001-2018 Subaru Impreza WRX STI Front 4 Pot Brembo Calipers
Should be installed by a qualified vehicle technician