I used the Ceramic Lightning Yellow Seal RC Car & Truck Bearings. I have almost a year with the bearings. As advertised “Maintenance Free", I had to clean the bearings on several occasions. They last long, but more the point is that Boca stand behind their products. If one or several of the bearings fail prematurely they will replace them, but you have to send the bearing directly to them as proof and then if determined that it was not due to user fault they will send the replacements.