Description The carburetor primer bulb has an overall diameter of 3/4″ at the base, and is just a fraction over 1/2″ in height. This is the size used most often on small recreational and motor scooter carbs. In addition, this bulb may be found on an endless myriad of small gasoline engines used on dirt bikes, go karts, ATVs, portable generators, weed trimmers, pressure sprayers, pumps, roto-tillers and a veritable plethora of portable utility and lawn garden products. A truly useful and ubiquitous little part. When you need it, you need it, and nothing else will substitute.