Hayes Dominion A4 MTB Disc Caliper Rebuild KitSpecifically developed for servicing your Hayes Dominion A4 hydraulic disc brake caliper, this kit contains the pistons and seals required to breathe new life back into your braking setup. Suitable for rebuilding one caliper. Genuine Hayes spare parts.Features: Use: MTB Compatibility: Dominion A4 Includes: Pistons and o-rings for servicing one caliper Genuine Hayes spare parts Manufacturer’s Part Number: 98-36140-K001Buy Hayes Components from Chain Reaction Cycles, the World’s Largest Online Bike Store.