Response from L.L.BeanBy jk, L.L.Bean Customer Satisfaction Team, December 28, 2021
The fabric is 100% Lambswool 5gg, 2 x 2 rib knit in the body and sleeves. 100% Lambswool 7gg, 2x2 rib knit in the neck rib, and 100% cotton basketweave 9.1 ounces per square yard in the shoulders and elbow patches