Insulated Foldable Lunch Bag with Adjustable Strap - Lightweight Portable Lunch Box for Men & Women - Perfect for Office, Work, Picnic, Hiking & Beach (Black Hard Fabric) - Keep Meals Fresh On The Go

A bit larger than I thought. Very sturdy.I got this because I wanted something that can be optionally flatter but can also get packed out. I don't need a day of cooling, just something to hold like a sandwich or salad chilled for a few hours. I don't even bother with Ice packs. It works grrat. It doesn't leak.I prep whatever the ight before, including a beverage, and leave it in the fridge open. Morning I toss in whatever would get soggy (pretzels, etc) and roll it up, toss it in my bag. by noon the drink is still cold, meal is chilled. It's a great lunch bag, not a cooler (again, I haven't used ice packs though).I've got a 16oz steel bottle plus a nalgene 32 and a couple Tupperware things plus a snack.Due to how thick the material is, if you only fill half of it and try to collapse it's it doesn't really want to collapse. But you could make it kind of. I'm not sure if id want to go this route for a messenger bag, but it's fine for a backpack.From my searches and trials, I'd say for a messenger bag you want 2 slim soft-cooler-type lunch boxes. Ratherz that's what I'd want instead, if I used a messenger bag. EDIT: the downside is soft-cooler slim things have zippers and leak. So I remember why I went with this anyway. It doesn't leak.EDIT: I noticed something when taking less food to work. The way the closure strap is attached, the top of the bag doesn't want to roll more than about once before it hits the strap attachment. In other words if it's not very full, it will create a better seal if rolled more than 1x. The front strap attachment should be lower, it would just solve that.That said, the 1x fold still keeps food chilled enough until lunch. Just something I noticed, would be and improvement.