Overall this is a very good gym bag! The straps are comfortable(I have about two miles of walking with this bag everyday), the top zipper and flap provide easy access to the contents, the material is stiff enough that it can stay open on its own. It also does well in the rain, I had a good walk in the rain and everything was nice and dry.

For my needs I wish the bag was slightly larger and that the accessory pockets had more space. When the main compartment is packed fully, is difficult to get items into the front pocket and bottle storage. For most users the size likely won't be an issue. I walk to work and have to keep my gym items and uniform items with me. That makes a tight fit when you factor in lifting shoes, deadlifting shoes, gym clothes, uniform, shower gear, and accessories (wraps, chalk, bands, etc). I can make it work, but I feel like a 40L bag is what this should be instead of 33. On days where I only need my gym gear this bag is perfect!

I'm not sure what the engineering aspects of the backpack are, but for how much I pack into this bag it does not weigh my shoulders down at all during my 30 minute (1 hour round trip) trip to the gym every day. Fits my 40oz Yeti in the side holder easily, my lifting shoes in the bottom compartment (NoBull flat shoes - though there's plenty of wiggle room so could fit squat shoes with bigger soles easily), my towel, protein shake, lock, over-ear headphones, wipes, etc. and there's still a bit more room if I needed to squeeze anything in. I've had to walk in light rain a few times and everything inside stayed dry, haven't tested in heavier rain but I'm not planning on walking directly in heavy rain anyways. Very solid backpack, highly reocmmend.