A microscope eyepiece micrometer is ideal for anyone wishing to take a measurement from an object that is being viewed under a microscope. This eyepiece is compatible with any microscope which has a removeable Wide Field 10x/18mm eyepiece (WF10X/18mm). To fit simply remove the original eyepiece from your microscope which sometimes involves the loosening of a small screw on the eyepiece tube and replace with the new eyepiece containing the micrometer. The eyepieces can be changed back if measurements are no longer required.Suitable for use with the following microscopes:Philip Harris M-100FX Monocular - B8R07235Philip Harris M-100FLED Monocular - B8R05547Optika B-151 Monocular Ecovision - B8R05554Optika B-157 Binocular - B8R05555Optika B-159 Binocular - B8R05564Optika B-191 Monocular - B8R05556Optika B-192 Binocular - B8R05557Optika B-193 Trinocular - B8R05558Optika B-150DBRPL Digital Binocular - B8R08120 Optika B-150DMR Digital Monocular - B8R05559Also compatible with these discontinued models:Optika B-50 MonocularOptika B-150DBR Digital Binocular Older Philip Harris Student and Advanced microscope models with a removable WF10X/18mm eyepiece