This is brilliant. I have worried for years how I would replaced the shorter-than-standard pop-up waste in our bathroom and this design solves every problem imaginable. It seals perfectly and feels as though it's doing so too, which gives confidence, and there's just the right amount of thread for the trap without it being too long (too low for my outlet pipe) or too short (can't get it to seal). I was puzzled as to how it might work, but mine (from ToolStation) came with an instruction sheet, which I'm posting here for the benefit of others. Apparently there are longer ferrules available for deep basins... I wondered if it might be better simply to supply a longer one that could be cut to length but that's just a thought and would mean more work on site. As it was, it took me less than 5 minutes to fit and test. As I said: brilliant!