That crazy looking pattern in the back of the jacket is O'Neill Firewall Magma. That's a thermal energy-absorbing pattern that absorbs and retains significantly more body warmth than a convential lining (like…25% more). It's printed there because the back of the jacket is THE place to keep your core warm. It is breathable and moisture-wicking too. Clever huh? This latest technology is the next level of warmth efficiency in outerwear and never moan about the cold again.