Was having a look on their website and they seem to have two specifications, Street and Race. Essentially it looks like the race version are more function over form and street vice versa.
I think I would end up ordering street version too, as I couldn't justify the small decrease in weight saving over the extra maintenance.
Options - Race, Street
Center Caps - No, Yes
Swiss* - Yes, No
Steel Inserts* - Yes, No
Hardware - Grade 8, ARP
* can be swapped between versions
Center Caps
Race version wheels are not machined to accept center caps as most tracks will not allow you to run them. The center forgings are then machined to be hub centric. Street version wheels are machined larger to accept our billet center caps that are hubcentric. Center forgings and center caps are vehicle specific as hub sizes vary.
Swiss
To remove unneeded weight additional holes are machined in between the lug nut wells and assembly hardware. This process makes cleaning a little more difficult.
Inserts
Lug nut seating areas are normally machined into the forged aluminum centers. However, in conditions such as racing where the wheels will be taken on and off many times stainless steel inserts add better life to the seats as well as a great surface to adhere the lug nuts too.
Hardware
Race version wheels are machined to accept grade 8 cadium hardware as it's less expensive and does the job fine. Street version wheels are machined to accept ARP stainless steel hardware as it will provide a better finish over time. Wheels utilizing the cadium bolts are machined to accept the nuts on the outside/face of the center where with the ARP bolts the nuts are located on the inside of the center.