S-398 is Made of 3/4″ steel tubing that is a total length of 6″ with a 4″ long 5/8″ key stock insert that has been machined for a no-wobble fit. The key stock with 5″ of grade 7 threaded rod drilled and tapped into one end. S-398-6 is a 5/8 key stock, 6″ total length. S-398-12 is a 1″ tubing, 12″ in total length. Comes with complete directions for installation. Strongest on the market.