Calibrate your 3D printer steps with this easy 1.00in. square block with a .750in. hole. Remember to use the 'Horizontal Expansion' in your slicer software settings to fine tune inside holes.
Curious - both my printers (I have a Pro TL-D3 Duel head and a Ender pro 3) and both of the Horizontal Expansion setting in Cura are set to -0.15.