Mystery Ranch is home to some of the roughest, toughest packs in the world, trusted to perform by firefighters, hunters, military and law enforcement. That doesn't mean they neglect the little things, as evidenced by the Full Moon hip and shoulder bag.
OK, it's a fanny pack, or if that's too anatomically specific for you, a waist pack, with the ability to convert it to shoulder sling carry. Spoiler alert: the Full Moon works well in both configurations. The wide nylon belt effectively distributes the load for comfort, which is good because the Full Moon can swallow a lot of gear. It feels bigger than its 384ci/6.3L rating, probably because of it's efficient rectangular design. There's no unusable space inside, unlike some overly contoured sling bags.
The Full Moon seems to know you're going to overstuff it, as evidenced by the fact that there's a foam pad and a hard plastic framesheet inside to protect your bony hips. Both are removable by turning the Full Moon inside-out and opening a Velcro closure. We see this space as also being useful for storing passports, currency and other sensitive items for travel. There is one external and one external zipped pocket for phone, wallet, etc.
One obvious use for the Full Moon is to carry layers on outings where the weather is iffy. A nice touch on the pack is the inclusion of two compression straps, so after you eat your lunch and don your layers, you can cinch the pack up. In practice the ability to convert to hip carry is indeed pretty useful, for example when mountain biking or cross-country skiing a shoulder bag will tend to rotate around under your arm, where a waist pack will stay in place. With the Full Moon you always have the option. It's a minimalist convertible hip and shoulder pack with maximum storage.