I use a $2 glass screen I picked up at a headshop and it works like a charm. Then again, I have an ash catcher so its perfect for me. I'm not likely to knock it out, after 2-3 bowls it get lodged in there pretty tight.

I would completely recommend it for anyone that wants to nearly double the number of hits per bowl, since it prevents pulling through. Also, if you happen to have a friend that rips a bong WAY too hard and constantly pulls the entire bowl through this is right up your alley.