The gear shift knob in a manual transmission equipped car or light truck is the large knob, usually made of plastic, that attaches to the top of the gear shift lever. Over time the surface of the knob can wear and you might wish to replace it to spruce up the interior of your vehicle. Many aftermarket manufactures offer specialty gear shift knobs. Some of these are made out of exotic materials such as leather or billet aluminum. http://www.gehm-carbide.com/cemented-carbide-insert-blanks/gear-sticks/