The 6x Vulcan is a good unit, as is the 4.5x. The FLAG tubes are L3 Filmless autogated tubes. I have yet to get one in that didn't have absolutely awesome specs. I'm not as big of a fan of the 2.5x and 3.5x Vulcans. A lot of commercial night vision sights have glass that is far inferior to that of the mil-spec units like the PVS-12 and Raptor. However, I was actually pleasantly surprised at how close the glass quality was. The mil-spec units still have a slight edge over the Vulcan glass wise, but the Vulcan is far lighter and more compact. There is also an 8x Vulcan now. If you have any specific questions, feel free to IM me or just post them here.
Thanks!
Aaron