Originally Posted by Bart
I don't know if generic plastic bottles you mentioned come in 3 oz sizes. What a TSO would most likely do is compare the unmarked container with a container of a known size. But 3 oz is the limit.
Three ounce bottles can vary. I have some one-ounce hair gel bottles that are much bigger than .9 oz bottles of shampoo that I have a ton of from my hotel stays. That's my point - who decides if a bottle is too big or not? If it's cylindrical it will look smaller than a flatter bottle.
But, in general, no problem using unmarked bottles? My plan is to use liquid toothpaste, hair gel, mouthwash, etc and just fill up the travel bottles from larger bottles at home.