This mirror was specifically tested and approved by VALOI and is well made, and importantly, it is flat on the back.Includes:1x VALOI Levelling MirrorThis mirror was custom made for us: 1 100mm diameter circle, with 6mm thick glass and safety edges to avoid you cutting yourself. It is unframed, so the perfect flatness of the mirror is preserved.To level your camera using a mirror:Get ready to scan with all the right things in the right place.Place the VALOI Levelling Mirror on-top of your whole setup (on-top of your Holder).Your camera should now 'see itself'.Turn on live-view on your camera/look through the viewfinder and focus on the front part of the lens.Adjust the camera position (tilt and pan) until the middle of the screen/viewfinder of the camera is in the middle of the aperture of the lens' reflection. The film and camera are perfectly parallel when the middle of the camera sensor sees the middle of the reflected aperture.(If you own the Advancer or the Adapter 104, use the levelling feet for micro-adjustments for a perfect result).Making sure not to change anything, remove the mirror, refocus on the film and scan your images.We recommend re-checking using this procedure every time you start scanning, and through-out a longer scanning session.