Wearable sleep sack. Soft bamboo material. Gently used, by the time we bought this my daughter was transitioning out of them. TOG (or Thermal Overall Grade) is a rating system that measures warmth and calculates how quickly a fabric uses heat. It is the standard when choosing the appropriate sleeping bag for your baby, depending on the ambient temperature in your nursery. We recommend a heavier TOG during cooler months and a lighter one during warmer months. TOG 1.0 = 69-73 degrees F