... guided valve and full open seat features great fluid flow through full open seat. The full open seat provides easier valve manitenance and seat pulling, in valve-over-valve fluid ends.Innovative unibody valve design ... parts are for Brewster, Continental Emsco, Ellis Williams, Gaso, Gardner Denver, Liners, Pistons, IDECO, National, Oilwell, OPI, Skytop, Wheatley, and Wilson VALVE AND SEAT FULL OPEN