Small fits ages 2–4, Medium 4–7, Large 7–14, and X-Large 14–18. If your kid is between sizes, go up, because the gauntlet needs room to fit over a puffy coat sleeve. For babies, infant gear comes in 0–12 months and 12–24 months, and if your baby is close to their first birthday, go with 12–24 so it lasts longer. The Infant Bundle (/collections/infant-bundles) includes mitts, booties, and a beanie for less than buying them separately. See the full size chart (/pages/size-chart).