It fits a 500ml water bottle, it fits a glasses case, it fits a wallet in the front pocket, and a mobile phone. It has 2 internal pockets in the main compartment to put your driver's license, etc. It has a convenient clip for your keys, where I put the garage keys and find them immediately. It also has a hidden pocket at the back, on the side that touches the leg. It is worth every penny for both cyclists and general use