they are 2 ozs and the lips are extremely secure. they are connected and snap down by pushing the middle. you can check them out on the BRU site for more spec's.
oh and one tray brings 8 containers. I'm giving 3 trays. I was able to store about 2-3 weeks worth of daily meals for my baby. but I'm sure that varies with age and intake. just to give you an idea.