The Synapse 25 Frame Sheet with the pull-tab open to show the t-bar behind the aluminum stay. The Synapse 25 Frame Sheet The Synapse 25 Frame Sheet installed in a Synapse 25 under a Cache.
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Synapse 25 Internal Frame


Current Title: Synapse 19 Internal Frame

Color: Black

Available Color options

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

We've retired the Synapse 25 Internal Frame so we can focus our efforts on other projects. You can sign up for our newsletter at the bottom of the page to receive updates on what we're working on next!


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

We present for your use these optional, removable internal frames with aluminum stays for the 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 Synapse—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.

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. 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.


.055” thick High Density Polyethylene (HDPE)
1” / 25mm wide 6061 aluminum
Nylon webbing


Synapse 25 Internal Frame: 9.6 oz / 272 grams
Synapse 25 Internal Frame: 9.7" (w) x 17.9" (h) / 247 (w) x 455 (h) mm
Rated 4.4 out of 5 stars
Based on 12 reviews
75%would recommend this product
12 reviews
  • Rated 5 out of 5 stars
    1 year ago
    5 Stars

    Great item!

  • Rated 5 out of 5 stars
    1 year ago
    Great support!

    I’ve been carrying the Synapse 25 for close to a year but without the frame, and now that I have one I can see why people find it so useful. It provides great shape and support and definitely prevents things from poking you in the back as you carry oddly shaped items- it was great for keeping the legs of my camp chair from bothering me. Amazing purchase!

    Maeghan M.
    Verified Buyer
  • Rated 5 out of 5 stars
    1 year ago

    Lucky enough to get one before TB ran out in the most recent re-stock, give me the additional structure I like in my S25.

    Allen H.
    Verified Buyer
  • Rated 5 out of 5 stars
    1 year ago

    I waited a long time for this item to be available, but it really helps make the bag more comfortable. Well worth the wait.

    Teddy L.
    Verified Buyer
  • Rated 5 out of 5 stars
    1 year ago
    Synapse 25 Internal Frame

    Just what I needed to stiffen up the backpack I purchased. Just as advertised and highly recommended.

    Kevin M.
    Verified Buyer
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