I'm running the Troy presently, like mvician said pricey, but worth it. I had the ARMS 40, but my scope wouldn't clear it so it had to go. In-between the Troy and the ARMS I tried the RRA Dominator II Eotech mount. I really liked this mount/buis, but again the scope came into play so I'm selling the Dominator mount.
Have you checked out the BUIS thread over at ARFCOM?
I don't mean to hijack....but on the topic of BUIS with EOTechs.....I have a Stag M3 with flat top rail and a EO 512. I want my BUIS to co-witness, which should I buy ARMS 40 or low profile? Do both flip up to the same height? Does low profile just mean that when folded its a lower profile on the rail?
There are a couple of options when it comes to BUIS. I only use folding BUIS so I can't speak to others like LMT, LaRue, GG&G and the infamous Chopped Carry Handle. Here are my very basic takes on the brands I use or am looking at.
Troy: Positive locking in to the upright position, average price new: $140 shipped, average used: $120 shipped.
New MI: Same positive locking as the Troy and they're offering a low profile version, running about $130 new for either version. Don't see many used versions yet.
ARMS #40: Higher profile and may not clear a lower mounted scope or magnifier. Runs about $109 new, $75-90 used
ARMS #40LP: Lower profile and will allow the bell housing of most lower mounted optics to clear. There is also a Same plane version that allows the large and small peep hole to be on.. the same plane as the FSP.
The detraction to the ARMS is that they are held in the upright position by a spring. This has caused failures to hold position in some situations particularly in the older (2 years ago) versions. Since I am led to understand that ARMS has put a stronger spring in the #40 series.
I have have 2 #40L-SP's and a regular #40.. none of which are on my go to rifles. I've had experience with them snagging in the upright position and pulling back, but not during fire. I'm using Troys on the go to rifles and the ARMS BUIS will all be replaced with either the Troy or the MI low profile BUIS.
There are a ton of options out there, but if you're familiar with the basic A2 type rear sight, most are intuitive and easily used. If you're looking for a pure co-witness option then you might consider just using a fixed position BUIS and save yourself 50-100 bucks.