The Marmot ROM Jacket is made of Gore Windstopper softshell 100% polyester fabric which is windproof and breathable while also being water resistant. The fabric provides generous stretch and some abrasion resistance while still being quite soft. It provides insulation while also being breathable and limits overheating and perspiration build-up by allowing moisture vapour to escape. The zonal construction divides this jacket into three regions: chest, side panels and the rest of the jacket. The chest region offers the most warmth thanks to the quick-drying polyester fleece on the inside (due to the need to accommodate the front pocket locations). Under the arms, the side panels are very thin and allow for maximum venting where you need it most when you are puffing your way up the skin track. The remainder of the jacket is the middle ground, Windstopper polyester. Put them together and you have a great combination of fabrics to cater to the different regions of your body. Top this all of with a durable water repellent finish (DWR) which offers additional weather protection from light rains.