The one under the barrel is a powerful green laser. I've read too many reports of the smaller lasers losing their alignment from the shock of a .308. Perhaps the better quality ones hold up but for now I'm trying this one out. I went with the Midwest Industries extension because of the reviews I've read on those and how well it fits and holes line up. They also make the extension with a full top rail requiring the front sight to be removed. But I will never remove my iron sights because I believe in a true SHTF situation if the scope gets bumped or damaged you can always yank it off and use the irons.Looks good, just a quick question, why two lights ? also what extension did you go with and why ? ( I am looking into putting an extension on mine).