This is a factory Kel-Tec CP33 .22 LR 33-round magazine. 

When you’re shooting .22 LR, the ammo can seem to disappear. These translucent 33-round factory magazines help avoid that by letting you see your remaining rounds and by giving you more of them! 

The unique quad-stack design maximizes capacity, while still allowing the magazine to sit flush. You’ll find cutouts on each side that can be used to make slight adjustments if the rounds are not seated properly, which is unlikely thanks to the anti-tilt follower.

So, if you like to shoot with minimal reloading to keep the fun going as long as possible, these magazines are just what you need.  

With the money you’ll save by shooting .22 LR, you can buy a few of these 33-round magazines guilt-free!