Perfect for short magazines, or to hang mags with a carabiner hook - Magpul Ranger Floorplate Magazine Accessory

If you have a short 5 or 10 round magazine, there's not much to grab when it comes time to eject. Tougher with gloves. These provide a place to grab those short magazines.

You can also use a carabiner to hang short or even long mags off you, a bag, a sling, etc. Beware they might make a 30 or 40 round mag hang too long to shoot prone or off a bench.

Easy to install. The PMAGs have a button in the center of the Floorplate. Push that button in the flat floor plate to slide the flat plate off. This is so you can disassemble to clean and service the magazine. Wear safety glasses. When you slide the plate off, keep a finger over it so the spring does not go flying.
Assembly is the reverse of disassembly. Slide the Ranger Floorplate on all the way on and the button should click in the center hole. Be sure each side goes into the grooves of the magazine.

These ship 3 of these to a pack. They feel very sturdy, like they can survive drops to the floor.