This is a Harris Engineering Rotating known as the Bipod, model SBRM.
Harris Engineering's Ultra-Light 6"-9" Bench Rest Swivel/Notched Legs Sling Swivel Bipod is manufactured using high quality parts to ensure excellent function and sustainable use. It attaches to a Sling Swivel Stud. Carrying your rifle with a sling or shooting off-hand is not impeded by the use of a Harris Bipod. Hinged bases have tension adjustment to eliminate tremor or looseness in the crotch area of the bipod. Bipods have an all-weather black anodized finish.
Features:
Legs Extend from 6 to 9
Notched Legs
Swivel tilts to compensate for uneven terrain
Hard Rubber Leg Caps
Attaches to a Sling Swivel Stud