Another prototype from Killen Custom designed for use on the airsoft HK416. He is now taking pre-orders... "Testing out the Killen Custom DD416 Rail prototype for airsoft HK416! Based off the Daniel Defense MFR HK4416 rail, it will fit AEG/PTW and TM next Gen 416 (dytac REM SMR barrelnut for TM required). Since not all 416s are created equal it might require slight sanding in some places, but this should be a rare thing.