This sipper mimics the natural feel, texture, and shape of a nipple, ensuring a close-to-natural experience from all angles. This design fosters effortless transitions, making the switch smoother and more natural for your baby. 2-STEP TRAINING: These sipper kits evolve with the baby's needs, suitable for ages 6 months+ and 12 months+. With Y-shaped and cross-shaped openings, On the premise of ensuring leak-proof and splash-proof, it fully meets the needs of flow intake at different ages. 6M+ round-head sipper, with its Y-cut design, provides a gentle flow akin to a nipple, facilitating a seamless transition to straw sipping. As baby grows, the 12M+ flat-head sipper, equipped with a cross-cut design and integrated diaphragm, helps develop your little one towards adult-like sucking patterns.