This Pondmaster Pump Diaphragm kit includes diaphragms, flapper valves, plastic slip washers and bottom pressure chamber gasket. Diaphragm Edge Wall must be inserted into the Diaphragm Retainer with the proper side facing into the groove in the Retainer. The deeper side of the Diaphragm will always face into the Retainer Groove. We are an Authorized Pondmaster Dealer!