Yep .750, and I've seen Syrac's gas blocks and heard good things about them. My issue is that Im thinking of a way to put back up sites on my gun which has a non-railed ff carbon fiber tube. I haven't seen, or heard of any good ways of attaching a rail to it, or if that would be a good idea anyway. So I was thinking if I get a railed adjustable gas block, I would be able to not only mount my iron sites, but also enjoy the benefits of an adjustable gas block. I know JP makes one, but Im trying to see what options are out there.