This 4-pack nipple bundle from MAM includes their innovative SkinSoft silicone nipples in both Fast Flow Level 3 and Extra Fast Flow Level 4 flow rates. The Level 3 nipples are designed for babies 4 months and older, while the faster Level 4 nipples are ideal for thicker liquids and babies 6 months and up. MAM nipples closely resemble the shape and feel of a mother's breast during nursing thanks to their flat, symmetrical nipple shape designed from ultrasound imaging of 16 breastfeeding babies. The nipples easily fit all MAM baby bottles and 94% of babies readily accept them. The SkinSoft silicone material provides a soft, skin-like feel and allows babies to feed at their own pace without nipple collapse. Together in this bundle, the two nipple flow rates allow you to adjust bottle feeding as your baby grows for a seamless transition between breast and bottle. The faster Level 4 nipples complement the Level 3 nipples for older babies ready for a quicker flow.