TOG is short of the thermal overall grade. The higher the tog rating, the more warmth your baby can get. Kaiya Angel 2.5 tog sleep sacks are double-layer with 60g polyester padding. You can pick these sleep sacks when the room temperature is between 16-20℃/61-68℉. As a warm, thick sleep sack, 2.5 tog is suitable for the baby to wear in winter.