I have 2 of these shells...in my experience with them they work well for a little while, but in the end they tend to have a problem on reset. They just seem to have a poor design on the seal that holds the gas. However I only have experience with these, and no other 40mm shells, so I give them an average rating.

One thing to watch out for... I fired the shell one time, and the o ring that holds the bbs in went flying with the bbs when i fired it. Luckily I was watching the burst, or I wouldn't have found that o ring again.