I'll just be honest, don't buy these. I bought four, (and got meu mags instead, not the flat base like the picture) and only one of them functions enough that I can say it functions. The other three wouldn't fill, and yes, I was doing it right. Tried propane, and three different cans of green gas and they wouldn't fill right no matter what. Do yourself a favour. If you have a co2 capable gun, buy co2 mags. Don't even spend the $25 on one of these just to try it. Run the other way, don't look back. They could be $15 dollars and they still wouldn't be worth it. No, they could be free and I wouldn't take them. Seriously, it's a money pit.