Hi I have received a email reply from the dealer that the long one is 140mm longer than the short one.
the length difference is just apply on the front fender while the share the same length of the rear fender!

one more question want to ask for advice!
I am choosing the wide of the fender, should I buy 60mm one ?

60mm will be to much for my original 26"*1.5 tires but if I upgrade my tires to marathon plus 1.75, then 50mm will be to less for cover!
Anyone tried 50mm for the marathon plus 26"*1.75???
i am listening to your opinion!
it is quite urgent as I want to order today for th Gilles fender!