The JAG35 Female Rod Clamp V2 is one of the two railblock options. The other is the Jag35 Single Railblock (male). All the edges on the single Railblock male have been chamfered (knobs included) and it comes with a smooth and precise milled aluminum finish that allows the industry standard 15mm rods to be inserted easily. The 1/4-20 set screw will allow you to attach any accessory with threading of the same size. The 1/4-20 set screw works with most camera microphones, sound recorders, and lighting equipment. another outstanding component of the single railblock male is the cross-knob located at the base of the 1/4-20 set screw the cross-knob facilitates adding and removing accessories promptly.