This is a Robinson Racing Extra Hard Steel 5mm Bore .8 Mod, 13 Tooth
Pinion Gear. These pinions fit brushless motors with a 5mm shaft and are
intended for use with the Traxxas E-Maxx model #3905. These will also
work with standard size brushless motors when used with the RRP1200
reducer sleeve, making them an excellent choice for the Traxxas Slash
This product was added to our catalog on March 15, 2010.
I dont know what this guy is talking about. I have had awesome luck with the 5mm bore pinions. They Never break or slip off. You never strip the grub screw cause it is 2 sizes bigger. All in all I have been running my truck real hard for about 4 months now and have never once had an issue.
Purchased this + Reducer sleeve for Slash 4x4 Set screw kept slipping off the motor shaft no matter how tight I set it, used blue loctite and same result, the pinion slid off and carved a pinion sized hole into my cover and chassis. Also the teeth sawbladed after 3 batteries on a plastic traxxas gear so I don't know how RR claims this to be hardened steel. Save your money and look elsewhere if you have a slash