This is a simple nose cone for a model rocket.

The nose cone in the .stl-file is for a rocket made from a cardboard tube with 18mm inside and 20mm outside diameter. (That would be a tube into which an A, B or C motor will fit directly.) These diameters and the length of the cone can easily be changed in the OpenSCAD-file. You can change the wheight of the nose cone by changing the fill percentage when you print it: if you need an heavier nose, print it solid, if not, print it with less % fill.