These rails work as described. They replace the stock 6" OPSGEAR plastic composite rails that come with their 416 hand guard (note: only the sides and the bottom. The top is not drilled for replacement). More durable, rugged, heavier, and fit most attachments better than the OPSGEAR rails. Wish they offered the package of 3 earlier...now I have an extra rail laying around and spent ten extra bucks.