Discontinued . A perfect chafe-free choice for warm conditions, Icebreakerand#39;s Nature 150 Siren base layer top is made from itch-free merino wool with a sweetheart neck. Available Colors: AZALEA, BLACK, HYACINTH, NAKED/MEADOW, BLIZZARD HEATHER/HONEYDEW. Sizes: S, M, L, XL, XS.