Gore-tex. When I forst heard it was being used in dry tops/dry wear I thought it was all hype. I said "theres no way its worth while, theres no way it can work". How wrong was I , its lighter and more comfortable to wear than any other dry top I have had, and it is mostly down to the materials. The other thing which makes it awesome is the fit, its great, comfy and not baggy/tight around the arms shoulders (which I have always found to be a problem). Lastly the Cordura reinforcement is fantastic at making my gear last through long jungle bush whacks.