Our 1.0 TOG Jersey Sleeping Bag (now with sleeves) is a year-round sleeping bag for an infant or toddler sleeping with their arms-out (usually from around 3 months of age). The Jersey Bag has a slim-fit, stretchy design similar to that of a swaddle and is recommended as baby's 'first sleeping bag' after the swaddling phase is over. The safe-sleep approved design is made from soft, stretchy GOTS certified organic cotton and bamboo viscose that is non-toxic and gentle of baby's skin. The ergonomically designed bag features a bell-shaped bottom to promote healthy hip joint development and is approved by the International Hip Dyslasia Institute, and the material is stretchy to allow baby to move more freely and stay comfortable while they sleep. The added sleeves provide a little more warmth on cooler nights, or for those whose body temperature naturally runs cooler.