Optimal-accessory-bag-to-carry-chargers-cables-&-other-extras-you-don-rsquo-t-want-inside-your-backpack-The-X-case-Medium-adds-2-8l-3-5l-of-packing-space-to-your-back-pack-Mounts-to-the-lumbar-curve-of-the-Boblbee-hard-shell-back-packs-Well-protected-&-insulated-with-aluminum-foil-to-keep-your-lunch-snack-fresh-Reflective-striping-on-all-sides-to-increase-visibility-Double-parallel-zippers-for-easy-&-quick-access-Compatible-in-size-M-2-8-l-with-Boblbee-20L-GT-GTO-GTX-as-well-as-previous-Peoples-Delite-model-Compatible-in-size-L-3-5-l-with-Boblbee-25L-GT-GTO-GTX-as-well-as-previous-Megalopolis-model