Perfect OEM Replacement & Compatibility -- Fits Mercruiser / Mercury Alpha One Gen II, Bravo & Blackhawk U-Joint Bellows. Directly replaces OEM part #91-818162 (also cross-refs Sierra 18-9870) for a reliable and correct fit. Damage-Free Ring Seating -- Designed to seat the aluminum retainer ring evenly and securely into the bellows groove—prevents twisting, misalignment or damage. Ensures a tight seal to avoid leaks and premature wear. High-Quality Machined Material -- Precision Integrated processing, High quality nylon material, built for durability and resistance to corrosion. Premium machining ensures consistent performance from first use. Saves Time & Hassles for DIY & Professionals -- Simplifies a tricky install step that otherwise requires forcing or improvising. With correct tool, retainer ring “drops in” cleanly, reducing installation time and risk of needing repairs later. Great for marine mechanics or boat owners. Affordable & Aftermarket Value Get OEM-level fit and function for less. Aftermarket tool warranties / quality assurance provide confidence plus less expense than sourcing OEM factory pricing. 91-818162 Bellow Retainer Ring / Sleeve Installation Tool – Direct Fit for Alpha One Gen II, Bravo & Blackhawk U-Joint Bellows – OEM Replaces 18-9870