Stock replacement. Compatible with Feuling 525, 543, 574 cam grinds and others with stock base circles. Fixed Length one-piece, which makes them stronger than adjustable pushrods. Made of 4130 chrome moly with swedged formed ends. Heavy duty 7/16 diameter tube with 0.165" wall thickness, precision concentricity, heat treated with a black oxide finish. Designed to eliminate pushrod flex, reduce valve-train harmonics and increase valve lift. Quick install pushrods are easier to use, however they cannot compare to a solid pushrod for strength and durability. Note: Since these pushrods fixed lengths they cannot be adjusted for other cams / engine set-ups than what they are designed for.