This is a New Set of one each 17, 18, 19, 20, 21, and 22 tooth Speedometer driven gears 0.77" OD. Part numbers 3987917 3987918 3987919 3987920 3987921 3987922. This fits most Chevy and similar transmissions with a 7/8" (inch) speedometer gear housing hole and 1.86 diameter Drive gear. Here at American Hot Rod Solutions we have many other gears in our other listings too. If you need help figuring the correct gear please let us know and we will be happy to help you.