Its completely waterproof, locks to the bike with one of those bike cables (it stays locked until you need to remove it) which i also use to chain the helmet on the seat, its huge! and takes 2 mins to fit. Was great at the motorcycle show, i rode their in full gear, had space to put it all in the bag and lock it and the helmet to the bike, then spend the day walking around in jeans and t shirt. The oxford panniers in these pics people rate- but they're **** in comparison.