The Substitute Board is the best way of indicating a substition during a game, in a professional manner.
The easy-to-use piece of equipment can be adjusted to show any number in red or green:
Diamond Football Co Ltd (T/A Diamond Soccer),
3 Island Farm Avenue, Molesey, Surrey, KT8 2UZ, England
Office Hours: 04:00 - 13:00 EST
T: +44 208 9419338