Originally got a FAL that had a SUIT on it. Israeli rebuilt/used as the tag on it shows they had it, for awhile. Problem on the FAL was the mount kept coming loose. Recoil and cheap rivets/sheet metal cover on the upper. The rivets would stretch/jar loose and I'd pound on them with a hammer/punch and it was great for a few rounds and then POI would wonder and sure enough, the rivets were loose again.
Took the SUIT off the FAL, bought an AR15 mount for it and put it on the last AR15 I was ever going to build (so I told myself and my wife).
It has a quad rail (that was the thing back then), an RRA light weight chrome lined barrel, I bought an RRA chromed bolt/bolt carrier for it at the same time/order from RRA, as well as an RRA match trigger. The rest is pretty plain jane AR15 stuff.
I bought an Aimpoint for it and just never was happy with the groups (red dots just don't work for me for stacking bullets on top of each other - or as close as I can.) I took the Aimpoint off and put the SUIT on the new AR15 carbine.
Old picture of it. Now has a Olight M21 Warrior hanging off the side of the quadrail.

The SUIT has a pointer that comes down from the top of the view (looks sort of like the Washington Monument, upside down) with the point/tip in the center of the viewing area. The originals also had a tritium source that lit the tip of the point up for low light conditions.
It has a lever on the side of the mount that allows the SUIT to be operated similar to the rear sight on the M16A1 rifles. Flip the lever one direction for muzzle to 250 meters (I think) and flip it the other way to raise up the front of the SUIT in the mount to shoot at targets past 250 meters.
The SUIT is also QD from the mount. Flip a lever and remove the SUIT to use the back up iron sights. Set it back in place and flip the lever the other way and it locks in place. In my experience a shot or two will vibrate the SUIT back to the ZERO. It might be off an inch or two at 100 yds. for that first shot. I never tried wiggling the heck out of it to see if it'll go back to ZERO that way.
The rubber eye piece is centered over the receiver rail. The objective lens is offset to the left side of the receiver.
I like them a lot. Bought another one and put it on the S&W M&P15 in 5.45X39 a couple years later. Now they are more rare and much more expensive.
Oh, I "relit" mine with a couple of those tritium tubes people use on their ends of their fishing poles for night fishing.
I also took them apart (neat how they're made inside) and cleaned them up, then adjusted the lens in the back when I screwed it back in to compensate for my aging eyes. The lens is pinned in place in the tube (multiple notches on the metal ring the lens sit in) to keep it from moving after adjustment.
Thought I had some diagrams/pictures of the SUIT itself. Can't seem to find them right now.