CMP Typhoon 500 Jet Internal [5" FD Mass Scal] [SS Gray] (23452 742 900) sundancespas and SPDT relationship gives this and SPDT relationship gives this timer its practical value because timing components need to match the original switching style and electrical role closely if the final repair is going to feel right The CMP Poly Jet internal is designed for compatible spa jet applications where a 3 3 8 inch face diameter roto style deluxe internal needs replacement The CMP Typhoon 500 jet internal is designed for compatible Typhoon 500 spa jet applications where a 5 inch face diameter massage style internal needs replacement Useful when the original internal is damaged or worn