Tamiya Centre One Way 18T 54051 not for trf501x???
 

The bag says that this is only for the WE edition, not for the original TRF501

http://cgi.ebay.com/54051-Tamiya-DB01-Alu.-Center-One-Way-Pulley-(18T)_W0QQitemZ120406734774QQcmdZViewItemQQimsxZ20 090416?IMSfp=TL090416159001r7991

But is this true? I thought they were basically the same car...

It probably only has the larger center pulleys that the worlds edition came with compared to the normal 501x.