1-9 are for Quarterbacks and Kickers, 10-19 for Quarterbacks, Receivers, and Kickers, 20-49 are for Running Backs and Defensive Backs, 50-59 are worn by Centers and Linebackers, 60-79 are reserved for Defensive Linemen and Offensive Linemen, 80-89 are usually worn by Receivers and Tight Ends, and finally 90-99 are for Defensive Linemen and Linebackers.