Norbert's 12cm quad bar mat system for 8' rails consists of four mats covered with 18 oz. coated vinyl material with hook and loop fasteners for easy attachment. 12cm mats are filled with 3.5" thick 75 ild polyfoam with a top layer of 1.375" crosslink for optimal footing. (17'6" x 17'6" space required.) quad bar mats are also commonly referred to as star bar mats.