I bought a camera bellows so the length can be easily adjusted without removing the lens each time. It's a little more money but worth it for the convenience. https://amzn.com/B00ACRH9RI

Another piece of advice is that you can actually close the aperture of your lens if it's body controlled. With lens attached set the desired f-value then hold the depth of field preview button while turning the camera off. This will keep the lens at the f-value you selected instead of wide open. This can be important because some fast lenses like a 50mm prime f/1.8 gives an extremely narrow depth of field on a macro extender. Closing the aperture some widens DOF.