If the oil in your Hypro D50 pump has lost its color, becoming a gray, milky substance then it's time to rebuild your diaphragm. The D50 repair kit has all the essential components required for a full diaphragm replacement, including four new check valve o-rings, two Desmopan piston diaphragms and the accumulator diaphragm. Each component is designed to be compatible with your Hypro D50 agricultural pump.