That's the center hole in the wheel. I had to search a bit to find some info on the reason why this is important. I pasted below what I found. Obviously, if the hole is big enough that what counts...
relates to the center hole in the wheel that centers the wheel on the hub of the car. Since most wheels are mass produced, they have a large center bore to accommodate several different vehicles. If this is the case, it is recommended that you use a hub ring. Hub rings are hard plastic or metal ring that fits between the wheel and the vehicle. This centers the wheel perfectly on the hub ensuring that there is no run out when the wheel is installed on to the vehicle. Without hub rings it is possible to get vibrations even if the wheel / tire assembly is perfectly balanced.
It's from a tire and wheels seller. They have great online tools to calculate fitment etc. : http://www.rimsntires.com/specs.jsp
It can be very usefull when searching for a replacement.
Originally Posted by rangersplash85
I'm not really sure what you mean by the core? The Hemi uses HD brakes, the V6 uses regular brakes.