what is the box on rugby players back

The small box or lump on the back of rugby players jerseys is a GPS tracking device that provides coaches with data on how much ground a player has covered, how fast they are moving, and where they are on the pitch. The device is part of a sophisticated biometric tracking system used by coaches to track a variety of player stats. The GPS tracker is usually inserted into a sleeve in the back of the rugby jersey and is designed to sustain collisions and impacts during the game.