Add-a-mat velcro ends allow mats to safely connect to other mat to "expand" and form a larger mat surface. CanDo accordion fold mats are durable enough for the school, gym and clinic setting. The accordion fold mats fold every 2 feet to minimize storage space when not in use. The 1-3/8" thick poly-ethylene (PE) foam mats are covered with 18 oz. tough fire-retardant  phthalate-free PVC coated vinyl; cover is sewn around foam. The vinyl coated nylon cover is strong, mildew resistant, anti-bacterial and wipes clean with a damp cloth. The mat is made with square side walls and is reinforced at all stress points for added durability. 1-3/8" thick Poly-ethylene (PE) foam has a hard feel and is used for more strenuous exercises.