This is a Harris Engineering known as the Adapter, model 2.
Harris Engineering's Bipod #2 is a Special Adapter for Hollow Forends. These Harris factory adapters are manufactured to specific tolerances to ensure a perfect fit between your firearm and your favorite Harris bipod. Whether you need a bipod for shooting in the field or off the bench at the range trust Harris to help get you the gear to fit your specific needs.
Features:
For Hollow Forends
Flange Nut
Single eyelet sling swivel stud
Creates an attachment point for bipod