Materials: .055” thick High Density Polyethylene (HDPE) 1” / 25mm wide 6061 aluminum Nylon webbing Construction: Made in USA with fabric from Korea / Japan / U.S.A. Specs: Weight:

Synapse 25 Internal Frame: 9.6 oz / 272 grams

Synapse 19 Internal Frame: 6.9 oz / 195 grams Dimensions:

Synapse 25 Internal Frame: 9.7" (w) x 17.9" (h) / 247 (w) x 455 (h) mm

Synapse 19 Internal Frame: 8.2" (w) x 15.2" (h) / 208 (w) x 385 (h) mm

Optional internal frames with aluminum stays designed to work with any generation of Synapse 19 or 25 that has rail loops.

We present for your use these optional, removable internal frames with aluminum stays for the Synapse 19 and Synapse 25 backpacks.

The frames are made of die-cut .055” thick High Density Polyethylene (HDPE), with a nylon webbing sleeve sewn down the center that encases a 1” / 25mm wide 6061 aluminum stay.

We’ve bent the stay to a generic spinal curve; we recommend you re-bend and/or adjust the curvature to best fit your own back (see here for instructions). If you just want a frame sheet, the stay is removable, though it's worth noting that a frame sheet sans aluminum stay does just about nada when it comes to shifting the weight of the pack onto one's hips. (Read more about that here in our Guide To Backpack Frames.)

Because the Synapses were not originally intended to accommodate an internal frame, they weren't designed with a way to attach one; this required us to make some modifications to the frame design. We took advantage of the loops for the Cache tablet/laptop sleeve ​at the top of the packs to retain the internal frame: a clever “T” bar holds the frame in place relative to the loops. The lower edge of the internal frame floats free in the Synapses—we’ve found this isn’t much of an issue as the contents of the bag tend to hold this lower extreme in place. Please note: your Synapse must have rail loops in order to use these new, optional internal frames. If your Synapse doesn't have rail loops, you're welcome to try using the internal frame anyhow; let us know how it works for you.

If you order the internal frame on the Synapse 19 or Synapse 25 pages along with the pack itself, it will come pre-installed. If you order the internal frame separately for an existing Synapse, or if you remove the installed frame and then want to add it back, take a look here: Video + Text Instructions On How To Install or Remove the Synapse Internal Frame

And don't worry: even with an internal frame in the Synapse, you can still use the very same loops to secure a Cache.

Once we engineered a frame for the Synapse 25, making one for the Synapse 19 was easy enough. You may be thinking: isn't an internal frame for a pack the size of the Synapse 19 overkill? One could argue yes and one could argue no, but really it's up to the person using the pack.

And, of course, we tested both sizes of Synapse with the internal frame on over a hundred miles of day hikes. Our take, after testing? The pros and cons of the frames resonate with our experience and the reasons listed below.

Benefits of an Internal Frame

• On bags with a webbing or padded hip belt, the vertical stability facilitated by an internal frame with an aluminum stay can help to lift some of the pack’s weight on to one's hips.

• It creates a hard back panel that prevents less-than-carefully packed objects like a thermos or DSLR from poking one in the back.

• It can prevent an overstuffed bag from barreling out against one's back.

• To some folks, a rigid frame against their back (with padding between the frame and their pack) just feels right.

Why You Might Not Want To Use a Frame

• A frame adds weight to a bag. Our Synapse 25 Internal Frame weighs 9.6 ounces / 272 grams and our Synapse 19 Internal Frame weighs 6.9 ounces / 195 grams. In many cases, you can forgo the frame and achieve similar benefits with careful and thoughtful packing.

• The rigidity offered by the internal frame becomes a liability when you’re squeezing your pack into the overhead compartment or under the seat in front of you, or when you’re packing your backpack inside other luggage. That's a reason it's nice to be able to remove the internal frame when you want to.

• Some folks simply prefer the feeling of a frameless or soft-back pack.

For more on our philosophy and experience regarding internal frames, please see our Guide To Internal Frames.