This is just a little jig to help splicing microphone cable (or other cable). The diameter is 0.3 inch, and length is 1 inch. There are 3 channels along the length to allow the spliced wires to maintain their separation. To use this, cut your wire to length by using the jig to help you measure. Twist the grounding shield so it can be soldered after the jig has been put in place. Solder and heat shrink the hot and cold wires. Put the jig into position and then solder the shield wire over them. Seal up with heat shrink (glue filled preferred)