This is a Magpul Industries Forend known as the MOE M-LOK, model MAG494-FDE.
The MOE M-LOK Forend is a drop-in replacement for the Mossberg 590/590A1* 12ga shotguns" featuring an extended length and front/rear hand stops for improved weapon manipulation. Now updated with M-LOK slots for compatibility with all M-LOK accessories" this Forend adds modularity to the proven Mossberg platform for sporting use" home defense" or on duty. Made in U.S.A.
Features:
Compatible with Mossberg 590/590A1 12ga shotguns
Reinforced polymer construction
M-LOK slots for direct attachment of accessories
Wrench included