I bought the medium Grid bag. It is a very sturdy and well constructed bag, but slimmer than I expected. Also, if you plan to hang a Garmin Varia off the back light strap, it will sag and aim pretty much down. You really need to be creative to fit much into the bag. I had to get a TPU tube and a smaller multi-tool, rearrange stuff a bit, but now have enough room for 700c TPU tube, multitool(with tubeless plugger), CO2 inflator, tire lever and Tyre Glider tool, and thin rubber gloves and paper towel . Anything more would require the large bag. It really locks into place under the seat. Varia needs to mount on the bike seat tube though, instead of the back of the bag.
I installed this on my mountain bike, an older hard-tail, and after some strap swapping it fit better than I had expected. I made a cardboard mock-up using their dimensions so I knew it would be close. I have cables under the top tube and was concerned that they might not work well going through the straps, but it hasn't been a problem. I've put a couple hundred miles on the bike and the frame pack has stayed put and performed well. I like the flexibility to shrink the pack if I want to, but so far it's stayed at the maximum size, and the movable divider really helps keep things organized. I carry an extra water bottle and snacks/lunch in the main pouch, and some things I might want when I first get to camp. It's convenient to get to without having to dismount and retrieve stuff from the panniers. I really haven't had a Blackburn product disappoint !
This is a convenient, compact way to carry the tools needed to tighten most of the fittings on a bike. It is sturdy and also has a spoke wrench and chain break tool. Not quite as important now with missing link connect chains, but if you were to ever break a chain you would be able to remove a link and fix it. A friend had this happen when apparently a small rock got lodged in his chain and separated a link from the pin. Unfortunately he didn't have a chain tool, so he tried press the link back in the pin using rocks. This worked but he could not put much pressure on the pedals w/o the chain coming apart again. I would not go on a weekend gravel ride or extended bike tour without this tool. It and a Leatherman Squirt (good pliers) should get you through most any emergency.
I chose this because it's big enough to hold a minipump (as well as spare tube, tubeless repair kit, tyre levers and a few snack bars), adds visibility at night (it's reflective) and has a clip for a light.
On all-day rides I put all the repair type stuff in the seatpack and then use a bar bag for convenience items - snacks, wallet, light layers. On shorter rides I skip the barbag, the seat bag is big enough.
The zipper can be a little stiff, and I didn't find the interior separator useful, it's easy to remove (just velcro).
I bought a 2nd seat bag for my 650b bike so that I don't have to switch out the spare tube when swapping it to/from my 700c bike. I've had the first bag for 2 years, it has travelled thousands of miles and it's still in good shape.
