This is a replacement nut for 1/4" Jacks with the "odd size" of 12mm diameter and 1mm thread pitch. This is slightly larger than most common jacks. These were commonly used on ZOOM processors in the 1990's era such as the 9030, 9050 and others; also used for some Roland products. The ZOOM specifically used Jalco jacks.

These are manufactured by E-lectronics in ABS plastic. If other colors are desired, please contact me as this is possible.