This carrier is designed for children who can already sit unassisted. It is most commonly used for back carry. Lenny BuckleOnbuhimo is available in two sizes Standard and Toddler.Standard size is a universal size of the carrier - it will fit an infant (who can already sit unassisted) as well as an older child. Toddler size is designed for toddlers over the age of two. However, it has a panel that can be adjusted in its width - this makes the Lenny BuckleOnbuhimo a truly universal carrier.