Use over regular sleepwear to take the place of loose blankets 100% polyester lightweight knit. Tog: 0.5 Size 2/3t fits 34-40" tall, and 4/5t fits 40-46" tall Generous sack design allows room for kicking, but cannot be kicked off so child stays warm all night Foot openings for mobility when awake. Room to tuck feet in at night Sleeveless to allow for ease of dressing and freedom of movement