This is the washer that holds the water in the toilet cistern. If cistern empties slowly on its own this washer can be the problem.
Replacement Spare Optima 49/ 50 Flush Valve Seal Washer For Siamp 34490507
3x Replacement Flush Valve Rubber Seal Washer For Siamp Optima 49/50 34490507
5 Pack Diaphragm Washer Replacement Compatible with Siamp, Inlet Valve Seals for Toilet Cisterns, Fits Side Entry Fill Valves
Toyvian Rubber Sealing Ring for Urinal Drain Pipe Gasket Washer for Toilet Waste Flange Connector Easy to Install Replacement Seal for Urinal Outlet Maintenance and Repair
2pcs O-Rings Seal Rubber Gasket,Bath Plug Seal,Sink Waste Basin Click Plug Clear Rubber Rubber Seal Washer Gasket For Push-Type Pop Up Sink Drain Plug Metal Basin Plugs(31/39mm)
WITEN&NOCK Shower Seal 2 x 60 cm for 7 mm 8 mm with Extra Extended Lip Shower Door Seal for Glass Door Straight Glass Door Thicknesses Replacement Seal Water-Repellent or Shower Cubicle Seal