that plus how much steerer there is above the crown. Best thing to do is measure the length of the steerer you have on your bike now and get a fork with the same size steerer. You may be able to cut the steerer down depending on what type of headset you have, I'm not 100% on that. I think you'll have zero problems as long as you get the diameter and steerer length correct. Someone please correct me if I'm wrong tho.