Evenflo CustomFlow Classic Silicone Nipples are made from soft silicone and feature Micro Air Vents. These special vents are designed to prevent nipple collapse and promote a more comfortable feeding experience for baby. Designed for easy assembly and leak- free feeding these nipples are compatible with all Evenflo standard neck bottles. Rest assured, Evenflo baby bottle nipples are 100% free of BPA, polycarbonates, PVC and phthalates, and are also made of FDA approved food grade material.