Originally Posted by
FBinNY
As Jive Turkey said, headsets are sold complete including the crown race. The only extra thing you might need are spacers in case the stack height of the new headset is shorter than the original. The flip side, a taller replacement than the original can be more problematic if the fork is too short.
One thing to check is that it's compatible with your frame and fork. Most bikes sold in the USA take ISO headset - 1"x24tpi thread, 30.2mm headtube, and 26.4mm crown race. However a number of bikes are JIS, meaning the headtube and crown dimensions are 30.0, and 27.0mm respectively. As I remember Specialized bikes, among others, were JIS for a number of years, so unless you have a Specialized the odds favor ISO, buty it's something to be aware of.
A taller headset (greater "stack height") can be a real problem if your fork was cut to just fit the original. Trek used to do this and I had problems replacing the headset on an early '90's Trek because the fork steerer was too short to accept anything taller than the OEM headset and there were no spacers to remove.
As to the JIS/ISO problem, what make is your frame and it's age? Older Japanese bikes were often JIS.
Edit: I checked Ritchey's web site and they no longer list any threaded headsets at all and the Amazon listing gives no info on either stack height or ISO/JIS configuration. I recommend you contact thae actual sellers (Either BikeWorldUSA or Niagara Cycles) to get the details before ordering.