Just to clarify, is it a RIS or a RAS you have for sale? If it is a RAS, I may be very interested. I probably want the #38 for $100 if it will fit a M4. I'm not quite sure on that length.
EDITED: Also, that last A.R.M.S. you have for sale for $100, does that have the flip up sight as well?
Additionally, when you say that it is the KA Aimpoint "straight" mount, you mean it is not the Offset Mount that they sell, but it is the Comp Mount? (Not the Cantilever, correct?)