Available in (SL) Single lined & (DL) Double lined. Identical features to TechnoButter with the addition of air technology. TechnoButter Air technology is a complex 3D structure of neoprene and trapped air. Think double pane windows, more air = more warmth. The TechnoButter Firewall inner lining is 20% Lighter and has 30% less water absorption resulting in the warmest, lightest and fastest drying material available.