Model Number: Microscope Objective RMS Thread Transfer to M42 Interface Adapter Ring Application: This M42 to RMS adapter ring transfers microscope objective RMS thread( microscope objective lens and some domestic microscope objective lens are RMS thread) into M42 interface. its objective thread is M25X0.75mm, it is not suitable for M42 to RMS adapter ring. So before you buy, please confirm which objective you are.