It's OK. I was given a bunch of these at World Cup in 2008 and I've used them here and there on my different guns. As noted earlier in the thread, they do need an extra o-ring to act as a cushion for the male end of the tank and form a seal, but this isn't really a big deal.
The only issue I have with them is how sharp they are. Seriously. The sides of the thing are like razors.
wts bko for cheap