Magpie Bipod Sling Stud QD Never used, still in box and sells for $129.95.

From the magpul site:

Optimized for rapid one-handed adjustments, the bipod quickly and quietly transitions between user configurations.

Designed to mount to the popular Uncle Mike's-style sling swivel stud, the Magpul Bipod Sling Stud QD attaches and detaches quickly and easily thanks to its rapid-attach mounting system. The self-locating, stainless-steel clasps ensure perfect alignment when mounting, and the non-marring, rubber saddle fits securely on most forends, providing ideal load distribution without leaving a mark on your rifle.