They stand upright when full and collapse small when empty for pocket- or pack-sized storage. The cap includes an integrated carabiner for attaching to gear, and the bottles are very lightweight when empty.
The collapsible bottles weigh under 2 ounces when empty.
They are promoted for outdoor and travel use—examples include hiking, camping, kayaking, and general travel—and can be attached to active gear via the cap carabiner.
They fold down small when empty so they can be stored in a pocket, purse, or backpack.
They are sold individually; each listing is noted as "Sold as 1 Each."