It is quite a large bag, Im 6'4" and it fits a full set of gym clothes, plus a towel and flip flops for the post shower, and there is still 25% of the bag free.  There is a solid-ish piece of material at the base of the bag to keep a rigid-ish rectangular base which keeps the bag sturdy, but sometimes makes it tough to stuff in a locker.  The zipper is large and strong, though zipping and unzipping is an occasional hassle since the fabric the bag is made of is very flexible so I need two hands to unzip this everytime as I hold the bag steady (another bag of mine unzips effortlessy and holds steady, made of a thicker sturdier material, but is more than twice the cost of this one).
It has 3 compartments, big one in the middle, side compartment with mesh casing, and another side compartment with mesh casing that has the expandable portion to store dirty clothes separatly utilizing space in the main compartment.  I wish it had an extra small thing up front for me to store little things like keys, phone, combo lock, deoderant, etc, as right now I have to go searching for it in the middle of the bag as I don't want to leave my keys and phone visible in the side mesh compartments.
Overall its a quality made product and it serves its purpose well, highly recommended.