Stone Glacier's Sky 5900 is a heavy duty backpack designed for hardcore backcountry hunters and hikers. It features a generous 4300 cubic inch main compartment while in "bivy-mode", but this can be increased to 5900 cubic inches with the addition of a sky lid. Internal carrying capacity can be further increased by 2500+ cubic inches with the use of a load shelf, bringing the overall internal volume to an impressive 8000 cubic inches. Regardless of the configuration, virtually the entire contents of the Sky 5900 can be quickly accessed on the trail thanks to a 22" front vertical zipper, and attachment points for swing out pockets can be used to carry small items. NOTE: This pack is the BAG ONLY. A Stone Glacier frame is required. Stone Glacier Sky 5900 Bag Only w/Lid Ranger OSFM 50017-RG-OSFM