Injector o-rings are vital to ensure proper fuel delivery, so don't use old rings if removing and reinstalling injectors. This kit comes with all of the necessary o-rings to do one injector. The scope of delivery includes the parts shown in the picture! If 4 nozzles need to be repaired, please also add 4 items to the shopping cart. Manufacturer Information about the manufacturer BAR-TEK BAR-TEK Motorsport GmbH Im Rauschen Auel 3, 51491 Overath-Brombach, Germany info@bar-tek.com