It started as just a blurb in a Twitter bio - "One of the seventeen Illini fans who cares more about football than basketball". But then it grew to become the IlliniBoard secret handshake. When you see someone else wearing the shirt, just give them a knowing nod.
Shirt is a Next Level Apparel 3600 Cotton Crew in Classic Orange. More details including the material blend and a sizing chart can be found on the Next Level Apparel website.