Threaded and threadless forks, Threaded forks have threads on the fork tube. Stock forks are threaded and you use a big nut to tighten the headset that threads to the fork. Threadless forks dont have threads and you need a threadless BMX headset, to tighten the headset you use a compression bolt and starnut thats inserted into your steertube, SR Threadless forks(more expensive ones) are threadless(obviously).