From the referral page "Owners who make 5 qualifying referrals will receive a set of 21” custom Arachnid wheels in black, silver or grey, including summer performance tires and installation. These exclusive forged aluminum wheels offer improved performance and are not available for purchase." I understand these are the same ones Elon has on his car so would be fun to have I bet. Getting the referrals is getting harder but they do look nice. I like how there are offering black as an option finally. Hopefully, they do this for the 19" rims as well some day.