Alfred, in the SLS PHOTO, #23 (or #20) show the "rubber (already) inside the metal cap". These are separable, at least in my car (may be #22 or #21, in which case the graphic representation in the parts pic is not very accurate.
Also, on my wipers, part #31 is a tiny o-ring that sits in a round channel in the wiper shaft. In the SLS photo it looks like a metal washer.
IMO, one cause of frozen wipers is water getting past #31 and/or under #23.
I just checked the EPC catalogue. It shows part #31 as a metal waher. I am missing that part, I'll try to get it. That little o-ring is not identified there so it maybe considered part of the wiper arm.