Assuming this is the bottle you have
I use the microwave bags when little one was small and it’s perfectly fine or boil water on the stove that’s what I did anyways then realised don’t need to sterilise 😂
@Frayere yess that the one thank youu x
@Ave thank you so much x
https://www.tommeetippee.com/en-gb/product-support/support-natural-start-glass-bottle