I've always tended to keep my designs as simple as possible and eschew adding features just for the sake of, well, just because we could. So, it should be no surprise that the first iterations of The Guide's Pack had no internal frame, just a padded back panel. The idea has always been to rely on careful packing to supply the bag with form and the user with comfort. I still think there is great value in learning the artful arrangement of a bag's contents to optimize weight distribution and therefore carrying comfort; however, as soon as I began using The Guide's Pack with my beta version of its internal frame and frame sheet, I started to see the light.
At 35 liters (when you include the side pockets), The Guide's Pack can definitely become somewhat heavy when fully loaded, and though not intended as a backpacking pack, it can certainly handle all you need for a very long day out (or maybe an overnight). Bending its single aluminum stay to roughly parallel my spine, I was able to comfortably lift some of the pack's weight off my shoulders and onto my hips (yeah, with just a 1" webbing waist belt). Combined with the HDPE frame sheet, the internal frame helps maintain the bag's profile (read: keeps it from beer-barreling when overstuffed) and also allows one to have a somewhat cavalier attitude when packing hard objects such as a DSLR camera or a thermos: basically, I no longer need to wrap them in extra clothing or some kind of padding to ensure all-day comfort on the trail. After some further tweaks and some long hikes, I was a believer.
The Guide's Pack’s internal frame consists of a unique, die-cut frame sheet of .060" high density polyethylene (HDPE) and a single stay of 1" / 25 mm wide 6061 aluminum. The stay is held in place by a strip of 2" wide nylon webbing sewn down the center of the frame sheet; you can remove the stay if, for some reason, you want a frame sheet but no frame.
You can also remove the entire affair: six flat "pockets" on the inside back of The Guide's Pack are designed to retain the six lobes (or fins) of the frame sheet. These lobes are engineered to relieve the torsional stresses of the pack flexing as you walk; they also facilitate the design that allows the frame sheet to be easily removed from the pack.
The aluminum stay comes to you pre-bent to approximate a generic spinal curve. If you find The Guide's Pack comfortable out of the gate, as most folks will, you're good. But if you need to adjust that curve, it's easy to do — and you needn't remove the stay or frame sheet from the pack to do it (we're working on a video that'll show you how — stay tuned).