Hydraulic disc brakes can only give powerful safe operation when their seals are working perfectly, allowing no air to enter the system, or any hydraulic fluid to leak or by pass the piston.
For other important items to help you complete a satisfactory brake service, try browsing the online 'parts list' fiche or catalogue for your model? You may like to check out what items other customers bought who ordered this item, listed below? This may assist in helping you order everything you need in one shipment, saving money at the same time!