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This Chrome Flip Top Basin Waste (1 1/4? BSP) will fit any standard basin with an overflow hole. Constructed from brass with a beautiful chrome finish, it is made to last. It has a flip top to allow you to trap/release water.
link:https://www.basindrain.com/basin-waste/flip-top-basin-waste-with-overflow.html
Flip top Slotted Basin Waste