proconnect! It's the best thing I have added to my guns since level 10! thanks a huge bunch to Tunaman ( firstname.lastname@example.org ) who got them for me (he can get them for anyone). You can't get them over here in the UK easily (I've certainly never seen them often here) but they are worth every penny.
They completely solve the problem of the residual gas left that can happen with level 10 when you want to take the valve out and are easy to use. Nice well made bits of kit. Tunaman even had the special fittings I needed to put it inline so that the proconnect wasn't right next to the valve spoiling the looks of my gun
here's a pic on my gun...