OK, I now have some of the o-rings specified by Parker. But I am confused. I have three attachments that connect to this tractor via the four male ISO 7241B connection points. All three attachments connect and work well. However, when I compare the o-rings among the three, the o-rings are not the same. They are three different sizes, and by that I mean more than just variations do to manufacturing tolerances. Does this mean that the internal machining (depth and width of o-ring groves) of the standard 7241B female quick couplers vary from manufacturer to manufacturer, but the couplers will work if you use the manufacturers specified o-rings?
My couplers are Parker, Alfagomma, and un-branded.