This is an authentic Cartier Panthère Medium quick release spring bar set (reference 37837855MM). It comes as a sealed set of 10 and is unused in the original Cartier International Service packaging.

The packaging is marked:
"BAR/SPRING
PANTHERE
37837855MM
Cartier International Service"

I have given you photos of this part from every angle. The pack in the photos is the exact one you will receive.

If you are not sure if this will fit your watch or if you have any other questions then message me.