Rock Shox Reverb Inner Sealhead It's a fact of life, seals will need to be replaced on your suspension with regular use. With regular use, your moving parts will start to wear out and will need to be replaced in order to keep your suspension working optimally. The Rock Shox Reverb Inner Sealhead seals the upper tube from the inner shaft as it cycles. It fits A1-A2 generation externally routed reverb seatposts. FEATURESManufacturer's part number: 11. 6818. 017. 000Seals the upper tube from the inner shaft as it cycles Fits A1-A2 generation externally routed Reverb seatposts | Rockshox | Reverb Inner Sealhead B1 Generation Seatposts