CamelBak is synonymous with hydration packs, and one of their flagship models since it was introduced back before dirt was invented – that's 1996, OK Millennial? – is the M.U.L.E., which used to stand for Medium to Ultra Long Endurance. We'll claim editorial privilege and omit the periods because, hey, they're annoying as hell to type, and even CamelBak uses MULE instead of… well, you know.
The version we're reviewing here is the mil-spec version, as in military specification. It's a substantially different design than the "civilian" version, and we were interested in it because of the flexibility enabled by the MOLLE system. Yes, another acronym: MOdular Lightweight Load-carrying Equipment, basically little slots that allow you to attach additional gear. Just search Amazon for MOLLE pouches and you'll see what we mean; there's something for everyone, from trauma kits to radios to smartphones to just about anything you can imagine.
So what did we want this for? Say it with us now: flexibility. The MULE is a great small pack to begin with. It's got just the right amount of storage for a day trip: some layers, water and food and basic survival gear. The mil-spec MULE adds a nice organizational pocket with pen sleeves and such, turning the pack into a great little overnight travel bag or classroom tote. Throw an IFAK on the back and keep it in your car for a go-bag, no problem. Another reason to have the mil-spec version is the durability: it's made from 500D Double-rip Cordura fabric and it can take some abuse.
The reservoir is the mil-spec CRUX model with a 3L/100oz capacity with the Quicklink system and a tube sleeve. There are a couple things we'd change: a thin sleeve to isolate the bladder from anything else you might want to stuff in that compartment, a slightly bigger and maybe padded sleeve in the organizer pocket to make it easier to slip a standard size iPad or other tablet into, and just a bit more give in the main compartment side to side and front to back. The MULE is built tough enough to overload, so why not just a smidge more space? All in all it's a beefy little go-anywhere do-anything 24 hour pack that's equally at home on a mountain bike or in back of an emergency services vehicle.