If you have the 2nd gen 155z/160ho that has the separate clutch cover and the removable oil filter in front of the clutch case then its a 16mm, if you have the first gen 155z/160ho which has the big one piece clutch cover then its a 14mm.
No worries bro, may have been just after the 6 plate clutch was introduced with the separate cases and filter, mine was purchased thru work when the new type(6 plate clutch and oil filter) were introduced and she has the 16mm. That's good to know bud as I had not seen one but now know. I stand corrected lol.