the z-pack is a dyneema ripstop shell. there are urethane caoted zippers.the stay is a hollow 1/2" aluminum stay that should not be bent. the shoulder straps are dual density foam, and the hipbelt is a single density open cell foam. carries about 27 lbs comfortably. i work at a shop and received this item for a very steep discount, eamil me if you would like to talk about the purchase.