Great sleep sack! Medium fits 6-15 months. See pictures for further sizing info. It worked so well for us! Perfect for my tummy sleeper as well - just put it on baby backwards. Excellent condition & comes in the original box. No rips, stains, or holes. From a smoke-free, pet-free home. From the official product description: Our weighted sleep sack is scientifically designed for self-soothing and sounder sleep. The gently weighted Zen Sack Classic calms like your embrace by providing comforting pressure only where babies are naturally held. This secure feeling eases the swaddle transition and helps babies self-soothe through sleep disruptions, leading to deeper periods of sleep that are essential for healthy development. ▪ Two-way zipper makes diaper changes a breeze ▪ Zipper covers, cuddly seams, and soft tags protect your baby’s skin ▪ Can be worn backward by tummy sleepers who can roll independently ▪ Grow-with me adjustable snaps ▪ 0.5 TOG comforts in all weathers ▪ The center weight mimics your reassuring palm and calms with only a few ounces ▪ The safe alternative to all-weighted sleepwear ▪ Applies gentle pressure that is tested for breathing safety ▪ Passes mandatory and voluntary children's product tests ▪ Tested for suffocation hazard, pulmonologist verified ▪ Hip-healthy. Does not hinder mobility Fabric details: ▪ 100% breathable cotton Care details: ▪ Wash in cold water on delicate cycle ▪ Tumble dry on low heat Sizing: ▪ 6-15months (16-26 lbs, 26-33 in)