This roof rack kit is designed for pick-up hard-tops/camper shells and trailers with an approximate roof dimension of 1425mm/56.1'' (W) x 1560mm/61.4'' (L). The Slimline II platform installs on the six (6) feet provided which slide into the original rails of your pick-up hard-top/camper shell or trailer. NOTE: Additional fasteners may be required to mount the original rails. No returns or exchanges.