Triblend
A fabric made of cotton, polyester, and rayon — drapey, vintage-looking, very soft.
Triblend fabric is woven from three fibers — typically 50% polyester, 25% combed ringspun cotton, and 25% rayon. The blend produces a drapey, lightweight fabric with a heathered appearance and exceptional softness.
Triblend tees became popular in the late 2000s as the "fashion tee" replacement for cheap heather grays. Examples include Bella+Canvas 3413, Next Level 6010, American Apparel TR401. They feel almost like a worn-in vintage shirt out of the bag.
Note for printers: triblend has a heavier polyester content, so dye migration (where the shirt dye ghosts through the print) is a real risk on dark colors. Use a low-cure plastisol or a polyester-bleed-blocker underbase to prevent it.