Rocky footwear with Gore-Tex booties keeps water out, yet "breathe" which let's foot moisture escape from the inside of the boot. This is where "wicking" socks come into play. "Wicking," means transferring or drawing moisture away from the inner layer of a sock to the outer layer of the sock. This drying sensation makes your feet feel more comfortable and enables the moisture to reach the Gore-Tex fabric membrane faster - allowing it to escape. Thermastat Liner is paired with a super warm wool and polypropylene terry thermal sock to create the Dry Knit System.