Suits 32mm & 40mm pop up waste, the top of the pop up is 32mm, the bottom is 40mm. If the basin has an overfow it will go thru the 32mm area, if there is no overflow in the basin, it will run thru the top of the plug and down.
When installing you need to take it apart & place in the basin and screw it back together.
When installing you need to take it apart & place in the basin and screw it back together.