This buy it now is for a set of two 930 wheel 13mm hub centric wheels spacers, factory part with 930 part number 93034161100. I have another set on here same part number and they are 21mm since these are 13mm I think they were shaved down to 13mm. 

Please see my other auctions for more great Porsche parts including 21 and  28mm 911/930 spacers.