Needed a speaker adapter for Morel tweeters in my 2017 Altima and sketched this up in Tinkercad. Should fit all 5th gen. models (13-18). Remember to use PETG or something else that won't melt in the car.

adapter dimensions:

83mm x 83mm
small hole: 51mm
large hole int.: 65 mm
large hole ext: 69 mm

Screw holes were a little tight so I drilled them out with a 1/4 inch drill bit.