It's an error in wemoto website I suppose.
anyway you can take this same picture, and I believe also same object.
Yamaha XT 600 87-89 Kickstart Oil Seal
If you r curious about this, ask them if they r the same part.
BTW, the last XT600 engine version has the clutch on right side, and right carter cannot be replaced with previous version, and has no hole. As a consequence, add a kick on a 2000-> model is NOT possible, and has no sense to write "kickshaft seal for XT600E 99-03"
SEE ALSO
Stammbaum XT600 3tb-dj02