As the Palace squad continue to be put through their paces throughout pre-season, supporters may notice that each player is wearing a small black bib. But why exactly?
Well wonder no more! The top contains GPS trackers which monitor each players' distance covered during the session, the speed at which they're running and heart-rate, allowing the numbers to be crunched to tailor sessions and help avoid injury.
To find out more about them, watch the video below: