I was all set to buy a whole new unit when I saw this advertised....Once the syphon unit is removed from the cistern changing the membrane is a doodle . Whole units are from £5 to £27... yes £27 so paying £2 for 2 membranes in a no brainer.... you don't even need to leave your house to get it. Of course if you only have one loo you can't afford to wait for the item to be delivered, but if you could source this membrane locally I'd recommend changing it rather than the whole unit.