Yes, the collar on the extension tube tightens up against the lower receiver. Armorer's wrench shown being used, though you can use any wrench that'll fit. Loc-tite isn't needed if torqued properly. Use molybdenum disulfide grease (I've used white lithium in a pinch) available at any auto parts store.
Parts 8 & 10 are what Big-Bore was posting about. Wear safety glasses.