King takes pride in the way their end cap seals against the body of the shock. Notice how the O-ring is located well below the threaded area of the billet aluminum end cap. This arrangement ensures that the seal can withstand the high internal pressures common to racing shocks. This configuration helps prevent leaks when the shock temperatures spike. The threads of each end cap are specifically timed to its matching shock body so the bypass tubes have the necessary clearance when installed on the vehicle. Numbers on each part ensure that the correct parts are used together.