Description says Retro should fit 4 months to 4 years, but I would say these are closer to toddlers - 4 years as they are too large for our 7 month old. Will probably go with the baby size and save these for future. They are cute though! Velcro strap makes them adjustable. I like the width on the back of the strap and they seem to be comfortable. The large frame size is a plus as the smaller lens type that we bought for our first child in the past just seemed too small.