MSD designed this 86403 Crank Trigger Ignition for Small Block Ford 289/302 and 351 Windsor engines. Four magnets secured in the aluminum trigger wheel pass by a stationary non-magnetic pick-up to trigger the ignition. This "flying magnet" design produces accurate trigger signals and the non-magnetic pick-up cannot be falsely triggered. This system will trigger MSD 6, 7, and 8 Series Ignitions and all MSD Timing Accessories. MSD 86403 Crank Trigger Ignition Features: Fits Small Block Ford 289/302 and 351 Windsor engines Color: Black Bracket Material: Billet Aluminum Wheel Width: 3/8” Sensor Dimensions: ¾” x 2.25” Trigger Type: 4X Diameter: 6.562 in. Pickup Included: Yes Crank Trigger Wheel Included: Yes Adjustable Mounting Bracket Included: Yes Hardware Included: Yes Quantity: Sold as a kit Street cruisers as well as Top Fuel dragsters trust MSD's ignition systems as the industry leader for over 40 years. MSD continues to push the envelope with cutting-edge ignition technology as well as intake manifolds and EFI systems.