The 1/4"-20 male mount has a locking wheel to tightly secure items such as external monitors.This Single Railblock will allow you to attach any 1/4-20 accessory to any single 15mm rod.1/4-20 works with most on camera microphones, sound recorders, lighting equipment and many other accessories.This Mount will allow you to attach any 1/4-20 accessory to any single 15mm rod. 1/4-20 works with most on camera microphones, sound recorders, lighting equipment and many other accessories.