Edit (5/29/15): After posting a harsh edit about this Thing's functionality (deleted) I have realized that it and similar products should be used as a handle, not a "through hole" loop type thing for your finger like I show in the pictures. If used as a grip, your index finger can still be used to properly index the magazine for quick reloads (however it does still put some distance between your finger and the mag well) instead of being stuck in the hole -- hate it when that happens :P
Replace your lame stock magazine floor plate with this cool, aftermarket accessory! Simply remove your old floor plate from your 9mm airsoft gun, and slide this one on as you would any other. Now you have a nice handle to pull on to whip a mag out of a pouch for quick reloads! Also has a widened surface on the end of the handle/base to provide a nice spot to whack to ensure the magazine is latched in.
Potentially useful if you are in a 3 gun competition or any other situation requiring a fast magazine change from some kind of stowed location. Theoretically this could be recommended for law enforcement users on actual firearms, but I wouldn't trust 3D printed ABS for anything my life depended on -- strictly fun. There are products out there similar to this Thing that can be purchased for people who would need a weapon to protect their/others lives, and this is not intended to substitute, replace, or imitate said product(s). Follow the order of the images for a visual demo!
Always follow proper gun safety procedures when handling or using anything that looks like a gun, including but not limited to: making sure that your simulated or real weapon is unloaded and not pointed at anything you don't intend to destroy while playing with or servicing it. Don't hurt yourself with it if it breaks and leaves sharp edges. It should be noted, however, that mine has held up well. Use common sense, just like anything else in life. You have been warned. Stay safe, have fun!