Sierra parts are machined to perfectly match the OEM part they replace, which gives trained technicians and DIY mechanics the confidence they need when making necessary repairs. Parts are also designed specifically to be of marine-grade quality to resist corrosion and provide reliable operation for years.18-2161 Applications:• Mercruiser: 45518A1, 45518A2, 45518A3, MC-I, R, MR, Alpha One & Gen II• GLM: 21140• Mallory: 9-72153 Reliable construction will resist corrosion For Mercruiser engines | Sierra Shift Arm For Mercruiser, Part #18-2161