Numbers on jonsered 2152 2252 clutch cover? 14, 12, 10?

[chunez]

Does anybody know the purpose of the numbers on the jonsered 2152 clutch covers? Also, does anybody know if you can swap a 2252 clutch cover on a 2152?

 

[huskihl]

They are for measuring the diameter of a tree that is legal for them to cut in certain areas of Europe

22 series covers do not fit 21 series saws