This is a Magpul Industries Grip known as the MIAD GEN 1.1, model MAG521-BLK.
The MIAD (Mission Adaptable) GEN 1.1 Grip is a drop-in replacement for the standard AR15/AR10 grip" now available in two dedicated configurations to fit most receivers. It is designed to improve ergonomics with interchangeable front and rear straps for personalized hand fit" an aggressive texture for positive weapon control" and is compatible with all Magpul grip cores to adapt to various storage needs. This update to the original MIAD has improved strap retention and also comes standard with the newest grip core that holds an included 1/2 oz. lubrication bottle. Two sizes are available- this TYPE 2 Kit (MAG521) uses taller back-straps for optimized fit with certain 7.62x51 receivers* and the TYPE 1 Kit (MAG520) which is required for most AR15/M4's as well as AR10-type receivers utilizing that standard. All mounting hardware is included. Made in U.S.A.
Features:
Improved ergonomics and positive anti-slip texture
Removable and replaceable front and rear straps
Custom waterproof storage of batteries