The Elusive 3rd O-ring

Copied from M. E. Martin's web page

Every time the rear tire is changed, it is time to replace the three O-rings which keep the moly paste in place. Two of the O-rings are immediately found, but one is not so obvious.
Part number 91358-MG9-003 (50.5mm x 3.5mm) goes in a groove adjacent to the splines on the final driven flange.
Part number 91304-KT8-003 (61mm x 2mm) goes on the shoulder of the wheel. An alternate number is 91302-MA6-003. You will see this one when you pull the final driven flange off the wheel.
Part number 91356-MG9-003 (39.5mm x 2.4mm) is the elusive third one. It is found in the final drive, where the final driven flange splines mate up to the ring gear splines. In the picture, a small screwdriver is shown stretching the O-ring a bit.
In case you need a reason to religiously replace the O-rings and lube the parts with Moly paste, here's what happened to Mike Sumner's splines. Contrast them with those in the first picture. $$$$$$$!