UA Siro uses a unique construction to give you greater stretch & recovery, ultra-soft feel & more breathable performance. Woven back panel for added durability & protection. 4-way stretch construction moves better in every direction. Material wicks sweat & dries really fast. Anti-odor technology prevents the growth of odor-causing microbes. Looser, flowy construction. Unique, curved V-neck with mock collar that lays flat. Raglan Sleeves. Piping details at hem & cuffs.