The Navien 30010604A is an outdoor vent cap for use with all of the NPE tankless water heaters:

NPE-180A

NPE-210A

NPE-240A

NPE-150S

NPE-180S

NPE-210S

NPE-240S

Units made before November 2014 did have a different vent kit (30010605A). 

Now, the item number 30010604A is good for all NPE models made after Nov. 2014.