I have found this product very useful - particularly if you have the Close to Nature bottles as this is suitable for the wide neck type bottles compared to other bottle warmers.
Furthermore, it has been recently advised NOT to make up formula feed and use an insulated bottle bag to keep them warm as at this temperature bacteria loves to breed. It is better to take the sterilised bottle with some milk powder dispenser and add hot water from the flask to it when you want the feed. If using breastmilk then chill in the fridge and use an insulated bottle bag to keep it cold then use the flask as a bottle warmer.
Don't faff around getting the electric version of this. This can do everything it can, have more uses, is cheaper and you are not stuck to find an electricity point everytime you use it!