These were designed off the original gears. We have hours of testing with these and work just as well, if not better than the originals. Also includes a tube of lube which is required to break in the gears. These will fit all US1 type chassis.  You get 3 sets of gears along with a tube of lube. Each set of 3 comes with a tube of lube. 

We have sold over 1,000 sets of these gears without any failures! Lifetime warranty on the gears also!