OK I've a few stems here so had a measure up, all mine are the taper bottom type not the split bottom type, all the measurements are to the tip of the taper:-
5."1/4 long marking line 2."1/4 up
5."1/2 long marking line 2."1/2 up
7."1/2 long marking line 2."1/2 up
8." long marking line 2." 1/2 up
11."1/2 long marking line 3" up
Hope that helps