The thread adapter is supplied with a special tool for mounting it on the camera. Once mounted, Leica correction filters from previous M cameras with smaller diameters can be mounted on the M10. The Thread Adapter also enables the use of the Leica Angle Finder M and the viewfinder magnifiers on the Leica M10. 

The essentials:

• Correction lenses from previous models can be mounted and used on the Leica M10
• Enables use of angle finder and viewfinder magnifiers