O-ring for the fork seal carrier (MG# 90706490)
Moto Guzzi V700, V7 Special, Ambassador, 850 GT, 850 GT California, Eldorado, and 850 California Police models
The size of the O-ring (MG# 90706490) used to seal the chrome seal carrier to the fork leg is ~49 mm ID × ~2.5 mm wide. Viton O-rings are best, but Buna-N work just fine and are a lot cheaper. Make sure to purchase an O-ring that is sufficiently soft...something with a Shore Durometer (A Scale) = 70 is great. McMaster-Carr part number 9452K141 (AS 568 A -135) works great.