PACK OF 1. Comet 1800.0020 Buna Diaphragm. Replacements for damaged or worn out diaphragms on the Comet APS41, MC25, MP20, and MP30 Diaphragm Pumps. A good indication that diaphragms on your pump need replacing is when you notice the oil in the sight glass is milky grey in color. Stop using the pump and immediately replace the diaphragms or else you can do serious damage to the pump.