The innovative Arisaka Zero Retention Clamp (ZRC) effectively minimizes zero shift for lasers and iron sights mounted on the handguard of the MCX Virtus and Spear LT. This particular model is tailored for the MCX Virtus in 5.56 and 300BLK and the Spear LT in 5.56 7.62x39 and 300BLK. Note that the Rattler is not compatible at this time. The MCX Virtus and Spear LT handguards lack sufficient attachment to the upper receiver leading to significant flexing. This can alter the zero of a laser or front sight when slight pressure is applied to the handguard. Pressure can cause a shift of 5 mils or more especially when using the support hand against the shouldered rifle. Furthermore the zero does not consistently revert to its original setting after pressure is relieved. The Arisaka ZRC features external clamps that screw into a specially designed U-bracket. This U-bracket connects to the extended upper receiver under the handguard securing the handguard firmly to the upper receiver along two axes thereby significantly reducing or even preventing zero shift. Importantly the U-bracket maintains the free-floating nature of the barrel since it does not contact the barrel or gas system. The clamps are designed to contour around the handguard ensuring minimal intrusion for the user's grip.Features include:- Compatibility with Sig Sauer MCX LT Spear Handguard- Precision CNC machining from 6061-T651 aluminum- Mil-A-8625 Type III hard coat anodized finish- Handmade in the USAFinish/Color: Anodized Subcategory: Handguard Accessories Fit: Sig MCX Model: MCX Zero Retention Clamp Model2: LT Standard