I think i've find it, this is this one??
http://www3.towerhobbies.com/cgi-bin...?&I=LXTBP2&P=7
Oufffffffffff, ouch!!!!!!!!!!!!!!!!! the wheel bearing

This wheel extender must put realy, but realy too much stress on the bearing
Do you have to run different offset wheel on front?? Why this adapter is not the same lenght front and rear????????