This is REQUIRED to install ANY fork onto your bike. You can remove the lower bearing and spacer from your OEM fork but it's incredibly difficult and you will likely damage them in the process. Save yourself time and headache and buy this kit so that you have everything you need. You will still need some special tools to cut your head tube and press the bearing onto the fork.
The CaneCreek ZS upper headset is required for most forks and will allow additional clearance for 21" wheels up front.
If you are buying a new fork from us we HIGHLY RECOMMEND having us install this for you.