Knights Armament Company or KAC has been making some of the best weapons accessories and weapons for the US Government during the GWOT. Originally located in Vero Beach Florida during the early years; their products with the Vero Beach Markings tend to be more desirable for people building clone rifles.
These covers are all new in the package with NSN. There is a separate website listing for USED Surplus panels.
Restocking on these are sporadic so be sure to get them while you can!