Deep See Thermo-Flex neoprene is a 4-way stretch material that stretches 3 times more than conventional neoprene. Thermo-Flex panels are located throughout the Quantum 5/4/3 to provide ultimate comfort and fit. 5mm neoprene in torso and upper thighs for optimum insulation. 4mm Thermo-Flex material in shoulders, arms, wrists and ankles for maximum stretch and comfort. 5mm Thermo-Flex material in sides of torso. 3mm adjustable skin-in neck panel to reduce water flow and improve comfort.