The ACE Folding Stock Mechanism with AR-15 Stock Interface allows for any AR-15 collapsible or fixed buttstock to be attached to an ACE Modular Receiver Block. This is accomplished by threading the user's preferred AR-15 Receiver Extension Tube, of either the Multi-Position Carbine or Fixed Rifle variety, into the threaded portion of the interface, securing it in the traditional manner via an AR-15 receiver extension lock ring. The Folding Stock Mechanism locks the attached stock rigidly into the open position with a firm yank, providing a very stable shooting platform. The stock may also be folded along the rifle's side at the shooter's convenience when maximum compactness and ease of transport are desired. Notes: This product is the folding mechanism with stock interface adapter only. Modular receiver block, buttstock, receiver extension, lock ring, and end plate are all sold separately.