I used baby bottles for my first to third children. The nipples deteriorated at the tip, so I bought new ones several times, but I used them less frequently than the bottles themselves. Especially the SS size nipples, I only used them for a month during the newborn period in rotation. The Bean Stalk nipples are one size from newborn to weaning, and I used these for 4 months. The M size nipples were used for 3 months. Bean Stalk Nipples x 2 (0 months to weaning) SS size x 5 (0 months~) M size x 1 (3 months~) The SS and M sizes are compatible with Pigeon's Mother's Touch nipples. Please note that when shipping the nipples, I will flatten the tips for shipping.