Check the listing for details. Ford Mustang 302 5.0 5.8 Cylinder Head Smog Thermactor Plugs SBF 351 TFS-5140026. Condition: New. Listed at 11.99 USD. This is a kit of 4 thermactor plugs for Small Block Ford engines (302, 351W, 5.0). These are useful when installing a pair of emissions legal heads on a non-emissions car. All OEM and aftermarket Ford smog legal heads have thermactor holes, one on each side of the head. Each cylinder head takes 2 plugs. Check out our other items if you only need 2 plugs. All OEM and aftermarket Small Block Ford heads have thermactor holes. These plugs block the holes for use on non-emission cars, and are internally threaded for accessory mounting. For use with GT40,GT40P, Trick Flow, World, AFR, etc. Compare to Summit Racing/Trick Flow at almost $10.00 PER PLUG! Some of these are silver in appearance, some are black hardcoat, all work equally well. Our customers say: "Great product at a great price, THANK YOU!!!!!" "Item as described. Excellent Ebay seller, recommend to friends." "FAST Shipping, Great Part" Thanks for looking! I added a picture of a plug installed in a head. This is the intended use of these plugs. These plugs do not work as 02 sensor plugs.This is a kit of 4 thermactor plugs for Small Block Ford engines (302, 351W, 5.0). These are useful when installing a pair of emissions legal heads on a non-emissions car. All OEM and aftermarket Ford smog legal heads have thermactor holes, one on each side of the head. Each cylinder head takes 2 plugs. Check out our other items if you only need 2 plugs. All OEM and aftermarket Small Block Ford heads have thermactor holes. These plugs block the holes for use on non-emission cars, and are internally threaded for accessory mounting. For use with GT40,GT40P, Trick Flow, World, AFR, etc. Compare to Summit Racing/Trick Flow at almost $10.00 PER PLUG! Some of these are silver in appearance, some are black hardcoat, all work equally well. Our customers say: "Great product at a great price, THANK YOU!!!!!" "Item as described. Excellent Ebay seller, recommend to friends." "FAST Shipping, Great Part" Thanks for looking! I added a picture of a plug installed in a head. This is the intended use of these plugs. These plugs do not work as 02 sensor plugs.