Women's Merino Wool Base Layer Bottoms Heavyweight Meriwool 400g merino wool bottoms by Filson Black (Black) 400g merino wool bottoms by Filson Black (Black) 400g merino wool bottoms by Filson Black (Black) 400g merino wool bottoms by Filson Black (Black). Thick moisture wicking merino wool makes our expedition weight 400g Merino Bottoms ideal as a next to skin base layer in the coldest weather, or underneath waders in icy rivers. The wool is from merino sheep, prized for their ultrafine fibers that are soft against the skin, moisture wicking and odor resistant. Wool has been natures top defense against cold, wet weather for centuries due to its ability to insulated even when wet. Front fly and elastic waistband.