This is the Magpul M-LOK Thumb Shelf.

If you’ve been searching for an easy and affordable way to improve your support-hand position on your rifle, you’ve found it!

Made from durable polymer, this shelf provides a textured indexing point for your thumb that helps improve control and recoil management without adding much bulk to your handguard. As a matter of fact, it only takes up a single M-LOK slot, leaving plenty of room for your other accessories!

Whether you’re outfitting home defense or range rifles, this shelf is sure to please!

At this price, you might as well order one for each of your rifles!