Double Nipple 1" -1" is used to connect two filter housings.
Double Nipple 3/4" - 3/4" is used to connect to filter housings.
Double Nipple Union is used to connect two housings
Connection is 3/4"
Straight push-in fitting is used to connect a hose.
Double Nipple 1" - 1" Brass - The Double Nippe is used to connect two housings.