Grubs CERAMIC 5.0 S5™ is the world's first rubber safety boot that uses non-matallic materials. This means it conducts neither cold nor electricity making them popular in a wider field of safety footwear. CERAMIC SAFETY TOE - complies with BS EN ISO 203450 S5 without cold absorbing/ emitting metal materials. DEFENDER™, 5mm Ballistic insole - lightweight and flexible whilst passing both BS EN ISO 20344: 2004 5.8.2 penetration standard and BS EN ISO 20344: 2004 5.9 flex resistance, without the cold of Steel. 5MM INSUFOAM-ULTRA™ NEOPRENE WITH CALF HEIGHT RUBBER - all round foot comfort and warmth 4mm rubber over the whole foot area makes it highly resistant to puncture and flex cracking. 6mm NITROCELL™ footbed - provides a soft cushioning for an athletic shoe feel. A million microscopic nitrogen bubbles that insulate the wearer from cold surfaces. TREDZ™(DURAPRENE™rubber) outsole - superior grip on a variety of surfaces, the tread is designed to work with the action of the foot, is oil resistant and passes TM144: 1999slip resistance test. COMFORT RATING - -20ºc to +20ºc HEXZORB™ Our HEXZORB™ technology, where an Hexagonal shock absorbing component is directly moulded into the heel of the outsole, to dissipate shockwave traveling up through the wearers leg. SUPER-DRI™ Wicking linings use thousands of fibre loops that cosset the foot and wick away moisture keeping the wearer dry and comfortable. Combined with 5.0 INSU-FOAM ULTRA™ to provide an unequalled comfort range without sweat and heat build up. UK SIZE BOOT HEIGHT (mm on leg) CALVE WIDTH (circumference in mm) UK6 380mm 410mm UK7 385mm 420mm UK8 390mm 420mm UK9 395mm 430mm UK10 400mm 430mm UK11 405mm 440mm UK12 410mm 440mm Grubs CERAMIC 5.0 S5™ Neoprene Waterproof Thermal Wellington Safety Boot