Neoprene Heat-Tech Warmth Swim SocksThese innovative swimming socks are some of the warmest available on the market, perfect for those who suffer from cold feet or swim through the spring, autumn or winter. At 3. 5mm they are slightly thicker than ZONE3s standard socks and come complete with a heat tech lining for increased thermal properties. A fantastic pair of socks to keep you warm and in the water for as long as you can manage.