Echo 1 MK1 SR 556 6.75" Quick Detach Suppressor MadBull has partnered with Echo1 to bring to you Echo1’s MK1 SR 5.56 Quick Detach Barrel Extension. The MK1 is a unique barrel extension because of its quick detach feature. This allows you to attach or remove the barrel extension in one simple step. The MK1 package comes with the barrel extension and flash hider specially designed for quick detach function. There are 3 lengths of barrel extensions. The 6” and 6.75” comes with a standard flash hider and the 7.5” comes with an extended flash hider. It is constructed out of T6 aluminum with a matte black oxide finish. Look no further for airsoft superiority and excellence, MadBull delivers all.