N Scale 1:160 5ea (the size is at best ‘nominal’ as Cowl Ventilators are the same from one you can hold in your hand to those big enough for your to climb into)
This is based in part on the Standard Pattern Cowl Ventilator as made to Classification Society Rules. The Cowl is 6,35mm/.250″ dia. The trunk (the smaller tube that goes into the deck) is made to connect to Evergreen #224 tubing. The trunk matches the tubing at .125″ dia. and has a small stud .069″ dia. that matches the tubing I.D. This way you can make the ventilator any height you desire.
These are somewhat special as Shapeways says they won’t print. What the mean is the reject rate is too high for them .. so .. these are a “One of a kind”.