Primer Bulb – 1/4in Inner Diameter Hose. This Atwood Primer Bulb is engineered and constructed to deliver the most reliable priming and long-term leak-free performance. The exclusive three-layer construction prevents collapse under vacuum and prevents ballooning or bursting under pressure. The low-permeation material prevents fuel evaporation, and this bulb delivers 60 percent more output per pump than leading competitors.Features: It is intended for use with a 1/4-inch interior diameter hose. Exclusive high-efficiency check-valves deliver faster priming and low fuel restriction less than 1kPa restriction at 50 liters/hour. Engineered hose barbs and stainless steel stepless clamps ensure leak-free performance. This bulb is compatible with Ethanol blended fuels, and it is EPA and CARB certified.