For some reason i couldnt get anyones links to work, so i couldnt see the treat bags. I think they are Great though!! I have been through Many classes with Riley, and wear the bag alot. I hate putting treats in my pockets! For one, some of my pants, the pockets are tight, so it woudlnt work. Also, i use smelly, soft treats, and those would just be gross in my pocket.
I have one that is pink, has a drawstring on the top so you can close it (great for agility so everything doesnt fly out, talking from experience here! everyones dogs had to stop and check out the treats at that jump!

). Has a clip to slip over your pants or pocket, or a spot for a belt loop.
I find that i have enough trouble keeping a leash, clicker, and 1 treat in my hands, let alone trying to hold more treats! A bag is great. Good luck in the classes! You will have a ball! I love classes!