Not sure of the exact application, but I got these from an old drag racer and have had them setting on a shelf for over 30 years. As far as I can see these are probably an obsolete plug.  2 of them are missing the screw on top cap. 14mm thread, short reach & 13/16 hex. Plug measures about .400" from the uncompressed gasket to the chamber end of plug, which probably makes them a 1/2" reach.  Note the "surface gap" which normally is used with a high energy ingition. Sold as a set of 3. Hope someone can use them!

Shipping costs are beyond my control.  I weigh the parts and try to select the most reasonable shipping methods based on size and weight.  I do not add a handling charge, nor do I attempt to make a profit on the shipping.

As always, these parts are available for inspection and for local pickup (to avoid shipping costs) at Lee's Speed Shop, 8320 Co. Rd. 52, Carver MN