Luth-AR Lock Pin Assembly for MBA-3 & 4 Only Black. It eliminates a weak point in ytheir stock and improves the lock up of your barrel. The small bend prevents it from rolling out and eliminates the need to overtorque or over-torque the lock pin in an effort to get a slight bend at the time you try to take apart your locked pin. This is Luth-ARs way of letting you overtorque the lock pin one time and having it last longer. You can't possibly get any easier than that. Specifications for Luth-AR Lock Pin Assembly - MBA-3 & 4 Only: Manufacturer: Luth-AR Additional Features: for MBA-3 & 4 Color: Black Package Contents: Luth-AR Lock Pin Assembly - MBA-3 & 4 Only Luth-AR RL-023B: Lock Pin Assembly for MBA-3 & 4 Only Black