Arc'teryx Men's Iridine Crew LS Helius (100% Polyester), Skytha (100% Polyester) Durable, quick drying, midweight fabric made from 100 polyester Soft Helius contrast ringer collar reduces collar chafing Gusseted underarms provide no-lift comfort Minimized seams increase durability and reduce chafing Provides sun protection (UPF 50+)