C7 ocular micrometer is used in place of the standard eyepiece of the microscope. There are two crossed rulers inside the eyepiece micrometer. Each ruler is 10mm long and is divided into 100 cells. Each division is 0.1mm.
If you need diameter 24mm micrometer, please to search Asin: B083W4QDCR
If you need diameter 20.4mm micrometer, please to search Asin: B09T9T2QFH