Fulflo is the worldwide manufacturer of hydraulic by-pass relief valves who maintains their high quality by producing all metal parts including housings, flanges, internal pistons, bolts, caps, lock nuts, bonnets, stop rings, etc. are manufactured, machined, stamped and assembled in our factory and made in the USA. Fulflo was established in 1912 and is celebrating it's 100th anniversary. Located in Blanchester, OH, Fulflo was incorporated in 1933 under it's present name and trademark. Patents for the original guided piston, direct acting relief valve were obtained in 1935, coincident with the onset of fluid power systems. The need for providing large flows without excessive bulk was subsequently met by the pilot-valve-control relief valve which was patented in 1943.