The Brass Animatronic Repair Starter Kit contains an assortment of brass gears curated by an animatronic repair professional. Gears identical in looks to the ones found in this kit are the most likely culprit of movement failure on an animatronic. You can verify one of these gears is in need of replacement when the gear has worn down and is not making proper contact with the other gears in the series (it's normal for the fit to be very tight!). Please bear in mind these gears are not recommended for replacing plastic gears (please search for the standard Animatronic Repair Starter Kit). Whether you're operating on the animatronic now or planning to in the future, the Brass Animatronic Repair Starter Kit is an essential addition to your toolbox. The Brass Animatronic Repair Starter Kit includes the following: -x3 brass 8T gears -x3 brass 9T gears -x3 brass 10T gears -x3 pulley gears -x3 small rubber belts The gears are versatile between larger scale and smaller scale animatronics, while the rubber belts that come with this kit are strictly intended for smaller scale animatronics. For larger and thicker belts, best for use in larger animatronics, please search for the companion Animatronic Rubber Belt Kit. If you have any product or technical questions, please do not hesitate to contact Skullkrane for guidance on your animatronic repairs, including tutorial videos, typed instructions, and more.