It's a bit of air pipe between 1-2 inch long with just 2 caps, one in each end (closed end in the pipe) push cap on to nipple and pinch the pipe behind the cap to insure it pops out then just make sure it's seated (you have a dozen or so ready in a box) it costs a £1 or so for a few feet of this air pipe
If you watch the vid
http://www.youtube.com/watch?v=pC5mwOJ2Khg towards the end you see the maker of the vid use the pipes to recap