This is our under rail barrel adapter for the M11/9 or M11A1 380. Rather than using the MPA upper bolt holes, it clamps onto the barrel land making it compatible with most any upper. Also you do not have to take it off to remove your barrel. It sets the grip directly below the trunnion rather than behind it to allow further spacing between hands. Lastly, we’ve incorporated a blast shield above the grip. This is a brand new variant Sam designed this morning and will be available for purchase soon (hopefully this coming week). This will also be an option for the Grey Ghost Upper Receiver. It will be sold as a set – Ace vertical grip and adapter or as the adapter alone. Please let us know if you would like us to notify you when they are available.