Roca Diaphragm Washer is an accessory required for closing the valve and regulating the water pressure within it when cleansing. This is a popular and genuine Roca replacement that will only fit on a dual flush valve. This top quality replacement seal is designed for use with the Roca D1D and D2D dual flush valves. It is a dry seal meaning no water is needed for installation, just a nudge fit. The AH0007100R is made of durable rubber and will provide a long lasting, reliable seal.