LOVE, LOVE, LOVE these cups!!! They are the cat's meow of sippy cups. The fact that they are well insulated allows us to keep a cup of milk out for our son to sip on for an hour and a half to two hours and the milk is still cold in that time frame! They don't leak at all because of the removeable check valve and "twist and click" technology. Our son can throw this cup around, leave it on it's side, etc and nothing comes out ever! We put them in the dishwasher and all parts wash up well and stay in great condition.