NSN: 8470-01-599-3851 Size: Fits Small through X-Large helmets Developed by Ops-Core, the ECH/ACH Improved Retention System (IRS) is a complete assembly in OCP Tan 499 to retrofit for ACH, ECH, MICH or Ops-Core helmets. This is standard equipment on the new Enhanced Combat Helmet that is replacing the current ACH, or a great upgrade to your current helmet. The system is adjustable for one-size-fits-all design. The straps are adjustable using ladderlock buckles that insure a snug fit to the chin and helmet. The attaching hardware (included) consists of four black ballistic steel screws and t-nuts that secure the IRS to the helmet. Unlike the old screws, these lock only require one-hand to tighten and won't backout. The IRS features a leather chin-cup and H-Nape pad for comfort. Nape pad provides optimal comfort for a snug and secure fit.