Hi there, it is the microphone.

:) Thank you @@GundogTV

Just looking again it's the the item on the zip on the bottom of Chris's Fortis training vest, his microphone is under his chin, the item has a hole in it and looks like it might be for dog leads. I have the same training vest and the only thing is lacks is a rings for dog leads to go on.

Hi there. The video is a clip of the full video that can be viewed on GundogTV gundogtv.co.uk/programs/rab-progress-no-whistle-752df0