The Crosstac Buttstock and Sling Upgrade Kit is perfect for upgrading military issue or LE slings with standard M4 A2 stocks that lack attachment points for HK hooks. Not only is this kit a fast fix to make your rifle sling compatible with any of the Crosstac Tactical Slings, it will let you improve a stock sling by adding the included HK hooks.FeaturesKit includes sewn web loop with captive D-ring attachment pointTwo HK hooksTri-glide loops to lock the hooks onto your existing sling