Are you worried about which weight sleep sack to use and whether your child will be too hot or cold while sleeping?With Woolino there is no need to worry because exceptionally breathable merino wool naturally regulates baby's body temperature to ensure s/he sleeps safely and comfortably through the night.This luxurious toddler sleeping bag will save you buying lots of different sizes and TOG ratings as it comes in one universal size that fits children 2-4 years old and it can be used year-round.• 100% natural: Silky-soft Australian merino wool lining & GOTS certified organic cotton outer. • Universal size: 2-4 years. Under-arm snaps allow this wearable blanket to grow with your child. 42" (107cm) long. • 4 season use - suitable for room temp. 63-78F (17-25C). Unlike any other fiber, merino regulates body temperature keeping your child warm when it's cold and cool when it's hot. • Both shoulder snaps for easy in and out. Full-length side zipper. • Zipper-pull guards to protect child's skin and prevent child from chewing on the zipper pull. • Closable seat-belt slots for easy transfer between stroller, bouncer, crib, etc.  • Nursery thermometer with dressing guide included. • Machine washable. • Woolmark certified merino. OEKO-Tex 100 certified fabric and accessories (tested for harmful substances). • Available also in Woolino 2-24 months baby sleep bag.Why Merino? A study done by University of Sydney, Australia has found that a better night's sleep is achieved when sleeping in or under wool. Significantly finer than other types of wool, merino is the perfect fiber to have next to child's sensitive skin. It breathes, regulates temperature, manages moisture, it is easy to care for, and durable. It is naturally perfect.