This is a hollow conical nose cone design for model rockets. The SCAD file is parametric - change the diameter and ratio (height to diameter) in inches and the program does the rest. Commented in the file are common diameters for nose cones. By using ratios, you can easily up or down scale any elliptical nose cone design for any diameter. Also included are three nose cone designs ready to print. See the instructions for favorite nose cone ratios. Please note - the NC-55BB nose cone is 8" tall including shoulder - make sure your printer can handle that size object.Simply change the diameter and ratio (in inches) in the OPENSCAD file for the nose cone you want to print and the file will create it. Some common and favorite elliptical nose cones are: NC-5S - 2.77 NC-20R - 3.74 (WAC Corporal Nose Cone) NC-50AR - 5.12 (has about a 1/2" cylindrical section - lengthen body tube of design by 1/2" to compensate) NC-55BB - 4.91 (Black Brant II)