I bought this bag because it is not to big but not too small, and it looks really clean. I can fit a 29 inch mtn bike tube, tire lever, crank brothers 19 tool, innovations air chuck and co2 cartridge. Everything fits nicely and i still have room for a 2nd cartridge. At first when I was out riding the bag slide through the strap so it was still attached to my seat but it was just hanging there, but once i got it good and tight and changed the position of the items in my bag its been solid and I havent had an issue. And for anyone like me who questions if the bag moves around since it doesnt have a strap for you seatpost like post other bags, dont worry this bag move way less than my old bag that had a strap for the seatpost.