FBIM is a professional football referee communication kit, 1200m talking range, support four people talking at the same time.
You can put the FBIM inside the armband case, in that way, you can run on the field freely.
This video teaches you how to pair three FBIM together, hope it could help you.
EJEAS store: [ Ссылка ]
P.S.: The FBIM could be bought from aliexpress and amazon, please refer to the brand EJEAS only!
