Original Cliff 1/4" mono jack, sealed blue. 4 PC mount terminals include: tip, tip-shunt, sleeve, sleeve-shunt. Threading: 7/16-20. Many types of professional music equipment nowadays use high power components, and need to be cooled by fans. Fans draw in dust and pollutants which can adversely affect the contacts of conventional jacks, with exposed contacts. This sealed jack avoids possibility of contamination of contacts by means of a sealing cover over the top and bottom of the jack.