Reliable sealing and anti-aging. Good helper for water heater, gasoline valve and various maintenance. Made of nice materials, it can be used for an extended time. Replacing the outdated one is a reputable choice. Type: Gas water heater accessories Colour: black Material: rubber Size: 54mm diameter Package Contents: 100 x stress diaphragm Only the above package content, diversified item shouldn't included. Note: Light capturing and diverse reveals can cause the colour of the thing within the picture a bit diversified from the real thing. The length allowed error is +/- 1-3cm.