These bags are made from very strong 650 gm  pvc. These gear bags are totally shower proof, the zippa has a pvc flap sewn over it then  its velcro down , this protects the zippa from rain ,dust and damage to the zippa . All sizes have the same features built in ,weather flap, grab handles, 2 in shoulder strap with 2 x 2 in side release buckles , 2 in webbing handles , a zippa pocket at front of bag (ideal for wallet or phone), extra webbing sewn around the bag for extra strength.This bag will handle extreme weather .