Bamboo Sleep Sack | Silly GooseMade from breathable viscose bamboo fabric. Temperature regulating for comfortable sleep. Ultra soft and ultra stretchy feel. Size 06 months 27" Size 618 months 37" Size 1836 months 40" TOG guidance: lighter for warm months, heavier for cool months. TOG 0. 5 shell: 95% viscose bamboo, 5% spandex. TOG 0. 5 lining: 95% viscose bamboo, 5% spandex. TOG 1. 0 shell: 95% viscose bamboo, 5% spandex. TOG 1. 0 lining: 95% viscose bamboo, 5% spandex. TOG 1. 0