Ok I am a huge rugby fan and have noticed that in the past few seasons there is an insert in the back of some pro's jerseys the lions have them and I was wondering if anyone knows what they are please.Ok I am a huge rugby fan and have noticed that in the past few seasons there is an insert in the back of some pro's jerseys the lions have them and I was wondering if anyone knows what they are please.

i think they r to track the players fitness n progress during the match....