Exhaust Valve Seat. Fits Big Twin 1966-1984.

* Easy oversize identification by the part number

* Easy to machine with cutter and stone

* Resists severe pounding and dissipates heat better

* Work-hardens during running-in

* Radiused for easier installation

* Replaces OEM # 18010-79

* Replaces OEM # 18017-66

* Replaces OEM # 18020-79

* Replaces OEM # 18055-66B

OD = 1.944"

ID = 1.575"

Thickness = .400"