The construction of the Water Sack is identical to that of Ortlieb's dry bags with a roll closure. The welded Ortlieb water valve in the base allows water to be released at a controlled rate. The large roll closure opening allows easy filling. The buckle straps can be used for hanging the Water Sack from a branch or hook, and the black version is especially well suited as a solar shower. The Water Sack is made of tear-resistant waterproof fabric and also features straps for suspension.