I am selling this because it didn't fit with my ARMS40A2.
I started to modify it as others have by grinding down the rear, but sopped when I realized it was a stupid thing to be doing.
I only got as far as removing the anodizing and the barest of aluminum from the tension bar. (see photos) If you use it with a GG&G BUIS, the non-anodized part should be hidden from view.
I also clamped a Larue mount to the rail and it left some scuffs there (see photos).
shipped 1st class (Paypal no fee) - new from GG&G is $85, some vendors have them for ~$75-77.