I used this as a gift, and it really helped the baby sleep well. I used it at night for 4 months. It's designed to fit up to 9 kg. It's a size M, but I used it from when the baby was a newborn, and as the baby grew, I used it with the leg zippers open. Please refrain from purchasing if you are concerned about it not being new. Please refer to the photos of the instructions. I will ship it compactly. White Lapin Popular model: Nekurumi