8 Pigeon Nursing Bottle Real SS Size Nipples My child was born in September, and I used these for about a month and a half. The ones on the left in the photo were purchased later (around October), and the ones on the right were used for about a month and a half. However, I was supplementing with formula, so I only used the bottles about twice a day, so the frequency of use was low. I sterilized them with a chemical solution, so there is some clouding characteristic of that method. I am very particular about items for my baby, and I only trusted myself. I didn't even let my husband wash the bottles, so I think I maintained good hygiene. (Of course, I disinfected the placemat used for taking the photos before taking them.) Are these suitable for those expecting twins? These are 240ml bottles, and you'll need to buy SS nipples for them at 3 months, so it might be a good idea to prepare 240ml bottles and use these. I plan to list about 6 S size nipples in the near future.