The #27 mount set adapts specific #2 housing types to the Nikon type microscopes. No modification to the microscope should be necessary. This mount set is a replacement for the #22 mount set. The #27 mount can be attached to all shutter types (LS or VS - excluding the CS45). A clearance cutoff (1.38in/35.1mm from the aperture center) is provided with the VS series only.