Check the listing for details. Replacement Pads for Mechanical Leak Detectors/Water Stop Valves - (18mm). Color: White, Condition: New. Listed at 8.99 USD. This three-pack of replacement water stop valves / mechanical shut-off leak detector pads are the perfect fit for nearly all systems on the market, from standard round, to auto-trigger rectangle designs. Once water comes in contact with the leak detection device, the pad is activated and begins to expand. As the pad absorbs the water, it expands to trigger the auto-stop valve in the leak detector, effectively shutting off the water supply. Simple and easy replacement with little effort for most systems. What's more, you can unfold the pad and use for additional clean up before re-arming your device with a fresh pad! Size:18mm Diameter x 10mm for a perfect fit to ensure the pad expands perfectly horizontal to activate the trigger! Our compressed expandable pads with wider design are designed to fit snugly inside the activation chamber of 17mm to 19mm models to ensure they expand vertically effectively triggering the shut-off valve. Other pads that fit loosely may not expand correctly, extending the time water is leaking before the device is triggered. This package contains THREE replacement pads ONLY. No leak detector devices are included.AROUND THE CLOCK PROTECTION: When water makes contact with the pad, our compact, dense sponge with wide base allows for full vertical expansion utilizing the full pad tray making it an express leak blocker for your system ROBUST THICK PAD: Our pads are designed to fit snug in each device. Smaller tablets may expand slightly off center and potentially not trigger the device properly 18mm wide fits perfectly with most 17mm-19mm pad leak detector / water stop valves. Compatible with EXPRESS WATER, AQUASURE, METPURE, ICON, or iSPRING systems. Will fit in thin pad designs that use 8mm high pads VALUE PACK of THREE replacement pads ensure you always have spares handy INDIVIDUALLY WRAPPED for ease and convenience