The nalgene wide mouth silo hdpe bottle is constructed out of high density polyethylene with a standard loop top cap the plastic is tough non collapsible and allows you to see the liquid level for quick identification the loop top cap ensures the cap stays attached to your bottle in extreme conditions you will never lose your cap again plus there are no leakages the nalgene bottle is bpa free and holds nearly 15 liters of the beverage of your choice and is ideal for any time anywhere use