One catch can is all you need! We made a few extra of these while making some for a few locals. This is the catch can we used in our video that shows you how to use only one catch can for both PCV ports on your MR16DDT. Designed to be installed under an Injen SRI or CAI, it hides away nicely. See the videos below for more information! Comes with all needed hoses to install as the video shows!