It has a female 36 TPI (thread per inch) thread at one end, which will hold any microscope objective with a standard RMS (Royal Microscopy Society) thread.

At the other end, it has a standard male M42mmx1mm male thread to connect to your 42mm adapter. 

Material: Aluminium

Height Size: 5mm 

Inside Thread:  RMS 

Outside  Thread:  42mm X1mm