8501X NEMA machine tool relays combine a rugged heavy duty design with modular construction for greater flexibility. They are ideal for applications where long life, high reliability and ease of maintenance are important. The 8501X relay family offers a complete line of relays and accessories for most control applications. This adder deck allows an addition four contacts to be added to a standard relay. The adder deck has the same straight through wiring as the basic relay. This makes wiring easier. The four plug in contact cartridges in this adder deck make contact conversion or replacement very easy. Contact conversion or replacement can be done without removing any wiring. This adder deck for an 8501X NEMA machine tool relay is UL listed and CSA certified.