These caps we upgraded in several ways to improve performance and longevity. We replaced the cheap bushing with a more durable bushing with a tighter tolerance for less play and more stability. We also use a multi ribbed Viton Seal on this which should last the entire life of the motor. You won't find Higher Quality Marine Parts We Only Choose The Best Materials Because The Repair Should Only Be Done Once. All End Caps/Glands are made from High Quality Aircraft Grade Aluminum Produced On Precision Computerized CNC Machines All Aluminum Parts Are Hard Anodized Using A Military Grade Type 3 Hard Coat (The Same Coating Used On Military Style Weapons) & Fitted With Viton & Or High Grade Urethane Seals Depending On The Applications Pressure / Sealing Requirements.