I purchased this bottle warmer and as others have mentioned, I put the correct amount of water in the chamber but sometimes it stills either gets the bottle to hot or it doesn't warm it at all. So I find myself going downstairs to get a cup to warm the water in the microwave and finish warming the bottle or getting cold water from the faucet to cool the bottle. This it what the warmer is for convenience but, to me this particular unit is not. Now that my son is on the AVENT 12oz bottles (he is only 2 months old so I skipped the 9oz bottles might as well buy 12oz and put the amount of ounces you need instead of buying 9oz then 12oz save money that way in my opinion) it will not fit in the chamber so I had to go out and buy another unit. I brought the Especially for Baby Bottle Warmer and its great. This unit warms the bottle just right not to hot and not to cold. So if you are going to be using the AVENT bottles I suggest the Esp. for baby bottle warmer.