Sierra's 18-7815 Diaphragm Kit is designed for use with select Mercury 7.5 HP, 9.8 HP, 10 HP, 20 HP, 45 HP, and 50 HP outboard engines. Includes one diaphragm kit per package. The kit is interchangeable with Mercury Marine 1399-5137 and 1399-5137B. Each Sierra product meets or exceeds the original equipment part it replaces. Fit specific, check part numbers to ensure proper fit.