The Attwood Multi-Layer Primer Bulb is designed to provide up to 60% more priming output than leading competitors in extreme conditions while exceeding new EPA requirements to prevent fuel evaporation. Attwood's exclusive three-layer design ensures high fuel pumping output in hot temperatures (up to 122°F) and cold temperatures (down to 18°F) while resisting collapse and hardening. Includes dual high-efficiency check valves that prime in any orientation with low-restriction fuel flow that ensures proper engine operation and aids fuel pump durability. Designed to exceed OEM engine fuel flow requirements.• Low Permeation Primer Bulb prevents prevents fuel evaporation• Exclusive three-layer construction prevents primer bulb collapse under vacuum and ballooning/bursting under pressure• 60% more output per pump than leading competitors• Provides faster engine priming and fewer strokes to prime• For use with 3/8" fuel hose• Operating temperature 18°F - 122°F• Tested to ABYC H-25 and USCG requirements• Engineered hose barbs are designed ensure leak-free performance• Designed to exceed OEM engine fuel flow requirements Exclusive three-layer design resists collapse & hardening Dual high-efficiency check valves prime in any orientation For use with 3/8"" fuel hose | Attwood Primer Bulb, 3/8" ID Hose