Great low cost competator to the kac rail covers - JE Machine Tech Handguard Rail Cover

Firstly, one should understand that these rail covers are not necessarily designed for any hand guard. Noting the metal tab located on the one end of the cover, these are designed to snap into place on specifically made notches set in certain hand guards. Knights Armament (KAC) designs their pic rails like so.
That aside, they will fit onto spec pic rails, but will not affix into place as intended. They are very form fitting, however, so no need to worry about them shifting on the rail. Due to this, getting them into position on your rail does require a good amount of force and leverage. If your rail is out of 1913 picatinny specs, I would not suggest using them. They are hard cast, and unlike Magpul or other covers like so, do not bend or flex.
They do have a bit of a slick feel, as, aside from the ribbing, do not offer much grip, due to lack of stippling or texturing. The ribbing does grip well, and, as one with large hands, fills out the hand guard to my liking.
If one is specifically looking for a military look for their AR build, this will fit the build, as stated earlier, for a much less then KAC products.