I bought six of these for a family rafting trip in the Grand Canyon. The non-plastic, food-grade stainless is great, just what I wanted. The cap is composed of two parts - a stainless plug containing the screw threads is attached to a plastic top which has the loop for attaching to your gear. We clipped the bottles to the raft, low in the boat, and I think they probably knocked around less than they would if hanging from a backpack loop. Half way through the trip, the plastic top had separated from the screw-in metal plug on three of the bottles, rendering them useless without a pair of pliers to unscrew the plug. Thank goodness we had our Camelbacks as backup!