There are different 'Challenge' wheels available, caution!
Its worth adding to this thread for anyone reading/considering these wheels is that there are 2 different types alloys available, both for different purposes, either road or pure racing.
There are the 18" 360 Challenge wheels which should have a BBS logo in red on them, these are superlight and where made for racing. They are generally usuitable for road usage as they are made from a very soft metal but greatly reduce unsprung weight thus improving handling, braking and acceleration considerably.
Then there are the 19" Challenge 'Style' wheels which don't have a BBS logo printed on them and aren't superlight weight. These where standard fitment on the Challenge Stradale and optional on the F430. While these wheels are forged (and still from BBS) they are actually rather heavy in comparison to the items made exclusively for circuit racing as they where designed to handle pot holes and bumps with more resistance the bending (hence they weigh more). These are ofcourse much harder than the pure racing wheels but aren't as super racing focused when it comes to unsprung weight.
Its worth noting that some people still run BBS 18" wheels on their road cars but they are taking a chance as they are very easy to bend.