This is an 18mm remix of Rick's Tiny Odd Rocket from Printables.com. https://www.printables.com/model/277658-tiny-odd-rocket/comments/402154#

I resized it in OpenScad to 17/13. That number is Odd but it allows for tolerances in the original model. This model will take boosters - we were launching it with a C6 booster to a B6-4 and it was doing very well. I made the first remix in all PLA and the second with PLA and a PETG motor can. Both work.

Just print it (print 5 fins) put on the top plate and nose cone (CA glue) being sure to align the launch holes. Then add the fins. Go play!