Below you will find two different versions of our Single Channel Gear Tooth Sensor. The 18ADS has a smaller magnet than the 37ADS. When you continue down the selection path, you will find it is offered in smaller housings. The 37ADS larger magnet version will see large teeth (4 to 12 pitch) to a farther gap. Click on the box that best fits your needs, and you will be brought to the electrical option choice page.