Wildcat MK3 A8.7 o-ring

Wanted to order a few more o-rings as a spare and checking for sizes saw an o-ring between barrel attachment connector (A8.6) and transfer port (A8.8)

o-ring part is A8.7

I have changed transfer port on my WC MK3 to a huma transfer port and don't remember that I have seen that o-ring inside transfer port

Does anyone know if is it really there on a stock WC?
I did notice that mine is just a bit different (ordered 04/2021) than fist ones from last year (rear of the air cylinder is different and air cylinder is a bit longer (only one of the dreamline extensions can be fitted as a power plenum, if two are fitted, air cylinder is longer than the end of the barrel so moderator can't be screwed on))

8.7.1627554025.jpg