Description 36mm one end and has a 21mm the other end (21mm is for the later VW dynamo/Alternator pulley nuts) Fan belt pulley nut spanner , much smaller and lighter than carrying a full sized 36mm spanner around . You are buying just 1 x 36mm Spanner , we also do the Pulley “C” spanner as well , see our other products . (In the other products we also do both spanners together as a set works out cheaper to buy both together) These are made from a tough tool steel then Zinc passivated .