This is a Ergo Grip Grip, model 4234-BK.
ERGO Grip's KeyMod Enhanced Angle Forward Grip is a multifunction KeyMod accessory designed to improve shooter comfort and performance. It can function as an angled forward grip or hand stop and allows for better weapon and recoil control
Features:
Enhanced thumb-over hold
Also can function as a handstop
6061-T6 Aluminum construction
Anodized black finish
