4236 is supposed to be for metric bikes
Order No. Ext Length Comp Length Travel Mnts. Spring No. Rate lbs/In
412-4236C 11.50 8.99 2.51 E/E 03-1315C 125/170
goto
http://www.progressivesuspension.com/productsearch.aspx look up s50 (you won't find s40) then look up any HD
metric bikes are all 42xx whereas sae are 40xx