Billet Aluminum Crank Trigger Wheel for Small Block Chevy. 12-Magnet Version that works with Innovators West Crank Trigger Sensor & Brackets or MSD. Application: Small Block Chevy 12-Magnet Version Uses High Quality Neodymium Magnets NOTE: This trigger wheel will only work with flange mount oil pump mandrels and pulleys with an OEM SBC 1.245″ male register.