Belfast (butler) kitchen sink waste, slotted type, complete with plug.
86mm (3.375 inch) flange. The outlet thread on this waste is 1-1/2 inch BSP - see BSPT link at bottom of page for more info.
We also keep a waste for a London sink. The primary difference Belfast and London sink is that the Belfast sink is fitted with an overflow which prevents water from spilling over the sink's edge by draining it away and down into the waste water plumbing.