Product review (3 stars): I did NOT buy this for the unit. I ...
I did NOT buy this for the unit.  I bought them because the 'W' washer was what I wanted and needed for another brand.  And the washer was exactly the same (nice that they had a ruler next to the cap, I could see that the washer would fit my unit.)  Saved me lots of $$ over having to buy the whole replacement from the OEM.  (I think the washers are really universal, but you cannot find them in any local hardware store.)