Calibration Cube 40x40x40

I'm very new to this. I'm sure to some veteran 3D makers this elementary. For a beginner, trying to make my first machine do what it's supposed to (or what I want it to anyway) this calibration tool has changed everything. Nothing was quite fitting until now. Everything I print fits exactly how it's supposed to now.

Made a new one that's a faster print and very little filament waste. The x&z arc should come out a smooth 40mm from corner to edge as you pass your calipers over the crescent