These are easy to use! Pop open the bottom, toss the right amount of water in and the parts in, use the microwave guide, and bam, sterilized!! A regular pen or perm. marker works on the 20x use tracker right on the bag, no mistakes here as long as you remember to mark it!
Which I love as I am using them for bottle fed kittens things, Ive always hated breaking out a big steamer and nothing else has worked quick and easy until these! And I can use them on the go, which feeding every 2 hours when theyre just 10 days old is amazing to clean anywhere I can find a microwave. And I feel ok tossing a bag after a kitten or litter no longer needs it as extra precaution.
Improvment: I do wish it had a collapsible 2oz cup or a line on the bag or something for even easier use for travel! For me, the bottles are 2oz, so its easy, but for busy moms, it would be a great improvement.