If you want a cheaper alternative than the stock ones that list for about $80 each, and that still looks factory and good, the plastic center caps that are from the 80 to early 90's Trans Ams/ Firebirds, that have the diamond lace or snowflake type wheels that are aluminum fit our T-Type rims. Just do a search on ebay for trans am center caps and you will find some reproduction ones that you can pick up for about $25 for a set of 4 and they are available in chrome or black and they dont have an emblem in the center. What I did was got a set then helped Mark from buickgn.com design an overlay that looks like the original Buick Tri-Shield emblem from the T-Type center caps. These overlays are now available on his site under center cap overlays and these caps/overlays look good when installed on the rim. If you would like some pics of them on my wheels I can take some pics and email them to you.