The top one is the Tailhook Mod2 and will be coming out in about a month. 5 position adjustable pistol brace, injection molded, proprietary buffer tube keeps it ATF legal. It's very nice! Will be under $200 for the complete kit. The bottom one is the Tailhook Mod1 and fit pistol tubes between 1.17" and 1.20", clamps right on. Some folks have run into size issues with their tubes because there is no standard for pistol tubes but he has ones he had made specifically for them on his site Gear Head Works
but you can measure yous and check it before you get a new tube. One of my good friends owns the company so I reap the rewards...lol.