This is the XCEL 6.5mm Thermoflex Flex Sole Scuba Diving Booties w/ TDC Technology Features: Fully sealed, maximum stretch seam construction that keeps water out Neoprene panels are glued and pressed together, then blindstitched (needle doesn&';t fully penetrate neoprene, keeping water out) TDC Thermo Dry Celliant, a revolutionary inner lining The ThermoFlex Flex Sole boot is an ultra-premium dive boot featuring all new TDC Thermo Dry Celliant, a revolutionary inner lining with Smart Fiber Technology that recycles your body heat into infrared energy for greater warmth, increased endurance, faster recovery, and enhanced overall performance. The boot is fully lined with TDC in a low pile infrared print. This boot features extended Flex Foot Protection, with a protective panel stretching from the ankle base to the toe. A puncture-resistant inner sole insert is sandwiched between the outer sole and inner boot lining for durable yet flexible protection.