100% Cotton Material: 100% Cotton, safe and healthy, super soft and comfortable. 2-way zipper for easy dressing and diaper changes. Detachable sleeve design, adjust as needed. Can be worn in two ways: Vest or Long Sleeve sleeping bag. Size: Small: length — 27 — for 6-12 months — baby height — 25-30; Medium: length — 33 — for 1-2 years — baby height — 28-35; Large: length — 38 — for 2-4 years — baby height — 32-40. Two types of thickness for you to choose: 2.5 Tog: 130g cotton filling, suitable for spring and autumn, room temperature at 59-68?H, 3.5 Tog: 270g cotton filling, for winter, room temperature at 14-59?H. Loose style, allows for kicking and cannot be kicked off at night, ensure your baby have a good sleep night.