NWT Sitka Merino Core Lightweight Bottom - Optifade Elevated II - XXL. New in package. Lightweight long underwear. With a gusseted no-bunch crotch and low-profile elastic waistband, the CORE Lightweight Bottom provides just enough warmth for when temps dip and dial up animal activity. Featuring permanent Polygiene® Odor Control technology to neutralize odor by stopping the growth of odor-causing bacteria and fungi. The CORE Lightweight Series is the next-to-skin layering foundation for SITKA Systems, actively moving moisture away from the skin while keeping the hunter dry and comfortable.