I ended up getting a set four 11-rib covers of P&S rail covers from Ebay for a whopping $27.50 - I don't know if they are Chi-com copies, or just surplus of the real deal. We had our M4's out at Drill this last weekend and we don't have Knights Armament on ours - ours are P&S, which apparently also got a contract to produce them.
In any case, the only rail position they'll lock into is the very last one - maybe it's wider than an actual picatinny rail slot, but they don't look half bad.
In any case, the only rail position they'll lock into is the very last one - maybe it's wider than an actual picatinny rail slot, but they don't look half bad.