Those that say that gold is better than silver should stay away from the Silver series of Spark motors. I abuse motors habitually. The Gold Sparks, while great gearmotors, were not up to the abuse I put them through. The Silver Sparks take the good features of the Gold Sparks(compact size and range of gear ratios), and take them to a whole new level. The Silvers retain the compact size of the Spark line of motors, and deliver superb level of reliability. I have never had a Silver Spark strip in the same application of other motors that have striped, even under stall loads, which are the most strenuous on any gear drive.If you are using these in a high shock load or high vibration environment, though, you may want to super glue/epoxy the gearbox plates inside the motor together, however, as they can come apart in such situations.