Lightweight And PackableUsing a waterproof and breathable ripstop fabric Endura have created a jacket that will keep you weather protected but won't weigh you down when it's not needed. It comes complete with it's own stuff sack so you can easily be stowed in a pack or pocket. With a central mesh back you get excellent breathability so you shouldn't overheat and start to feel clammy. WaterproofMeasured in mm of water that can be held by the fabric without leaking. 1,000mm is the minimum measurement needed to pass the accepted definition of "waterproof". For a garment to be truly waterproof, the seams must be sealed (in addition to the fabric itself being waterproof). All Endura waterproof garments are 100% seam-sealed. BreathabilityMeasured in grams of moisture that can pass through a square metre of fabric over 24hrs (g/m2/24hrs) using the B-1 inverted cup method. All Endura waterproof garments are fully "breathable".