I see there are a bunch of diffrent letter next to the holeshot tires and I was wondering what the diffrence where? which is a good all around model, which wil last longer and so on.

This is for a 03 Z 400.

Also is it ok to run these on the rear and the stock tires up front?

 

www.itptires.com/

In my experience the Standard Holeshots are nice and light (good for smaller bikes), but wear kind of fast. My favorite are the XC's. They are closest to the stock size (you can keep your stock gearing). XCT's are taller for better ground clearance. XC's and XCT's are 6-ply rear and 4-ply front........indestructible. Standards are 4-ply rear and 2-ply front.