Our 5 port design has no downward facing port which helps eliminate dust signature when shooting in the prone position as well as acting as a compensator. Our Redesign of the YHM-5M2-QD has a smooth sleek look which eases cleaning. The redesign also features an improved mounting service which makes attachment quicker and easier. - The YHM-5M2-Q.D. is threaded 1/2-28
Determined at checkout.