Kibblewhite Black Diamond Exhaust Valve For Harley Features: All Kibblewhite Precision Machining, Inc. stainless steel valves are impregnated by a special German process with a .002 deep & .0002 surface build-up to improve wear properties and reduce friction This improves wear properties, reduces friction, and provides resistance to corrosion and wear that is superior to chrome and nickel electrolysis plating Designed using Finite Element Analysis software, and profiles are tested on our computerized flow bench Black Diamond Valves are light, strong, one piece forgings with profiles that provide excellent flow characteristics Head Diameter: 1.570/39.88 mm Stem Diameter: 0.3384 Tulip: 29 Overall Length: 3.510 Remarks: Standard Head Diameter: 1.630/41.40 mm Stem Diameter: 0.3384 Tulip: 29 Overall Length: 3.510 Remarks: Oversize