You can choose to rebuild forks in two ways; buy the complete fork-leg assemblies, the easiest but probably the most expensive, although time saving - or - you can rebuild using only the sub-component parts you require. If the forks have suffered accident damage then renewal of the complete assembly would be the preferred choice, if however it is just a case of long term wear and tear then the latter action would be the sensible choice.
This part and those listed below maybe required depending on which course of action you have chosen to pursue: