The ½ zip on our Performance Blackcomb SUW Top makes this base layer even more versatile. Zipped to the top the turtle neck collar seals in warmth when temperatures start falling. When the sun comes out and temperatures start to rise, unzip the collar to let heat and moisture out and dry, cool air in. The ½ zip combined with a slim fit also provides a fashionable, sporty look. Seamless body mapping strategically engineers warmth and breathability zones where they are needed most while the use of recycled PES material helps keep our planet green.