Backpack Stone 42 Duffel. When easy access to your gear is paramount, the Black Diamond Stone Duffel offers simple and easy accessibility with an emphasis on lightweight comfort. Featuring recycled fabrics in the pack’s body construction, the Stone Duffel has two internal pockets to keep your essentials organized, while the full-length zipper provides ample access to your gear. Plus, a removable rope tarp adds cragging functionality.