After having three children, I learned very fast that sippy cups disappear into think air. I don't know why, is just a fact of life. I bought a pack of these cups to keep around for just in case. I placed one in the diaper bag, and car and at some family members homes. They were cheap and perfect.
My son wanted to use these one day, so I let him. First thing I did notice is they are not spill proof as they say. The first thing my son did, was tip this cup upside down, and it dripped out. It wasn't to bad, just slow dripping. I expected that though, so I wasn't really disappointed.
They are very easy to clean since their is no valves on it. The cups are 7 ounces and there are 24 cups in the package. I think they are a good value since so many are included and very nice to have in a pinch. I wouldn't use these as every day use though, since they do spill. They are cheap so if you want to throw them away while you are out with your child, you can do that and its one less thing you have to carry around with you.
I would recommend having at least one pack of these around the house and having some in the car. They are a great value for the money you spend.