Three 60mm long (in direction of calibration) rectangles with letters to denote which came from which axis. Print slowly and hollow all at once with single walls and calibrate your X, Y, Z, axes and get ideas for improving your Extruder, Cooling, and Bridging! 1 cheap print does it all--total weight of hollow was .3 OZ!
Each rectangle measures 60 x 10 x 10 in various directions.
(Sorry for my not up-to-par print quality)
Go for the extremes! Print with 1 shell, and print hollow. Set your cooling settings to keep the z print going strong. One picture is included where I used no cooling at all...what a mess!
My X, Y, and Z axes are SPOT ON now!