Eddie Bauer black & grey nylon. Soft construction, zipper compartments on each end with disc vents, mesh-vented zipper pocket in front. Elastic stretch cords outside on top, 4 carry handles and assorted metal rings for a shoulder strap that I don't use, also useful for attaching to bike or scooter with bungee cords. Zippered mesh compartment inside, 3 Velcroed mesh pockets.
Of course my high school gym bag in 1963 was green cotton canvas with no pockets and 2 simple loop carry handles, just a single zippered compartment with a stiffened bottom, you threw everything inside loose. Used it during my first years in the Army until it disintegrated, probably from rot caused by leaving wet towels inside it too often. But hey, I assumed cotton canvas is naturally breathable, more or less.
Well, that was gym bag technology over 50 years ago. This thread makes me wonder if today's things sometimes get overthought in their design, full of too many "features". But it's hard to resist their appeal when you're out shopping. I wonder if I'd go back to a simple canvas satchel-style if I saw one in a store today?