1/8" Female to 1/4" Male Adaptor
Required for many headphones to be compatible with professional audio equipment (Headphone Amplifiers, AVID MBox in sound rooms)
NOT Required for all recording devices such as Zoom H4N and Tascam DR-60DMKll
Some have threading on the 1/8" side, some do not: consult your headphone jack to see which you need as it will not fit on with the wrong kind