6.35mm Jack connectors have become industry standard on many types of consumer level and professional audio equipment. They come in a few shapes and sizes, so it is important to know what you are looking for.

Instrument / Guitar leads use a 1/4″ mono Jack, iPod headphones use a 1/8″ stereo jack, and balanced mixing console outputs usually require a 1/4″ stereo Jack.

There are both mono and stereo versions of jack connectors, know as TS (Tip, Sleeve) and TRS (Tip, Ring, Sleeve) respectively. It is easy to identify the two, with a TS having one black insulation ring on the plug, while a TRS has two. Typically Tip carry the hot or the left signals, Ring carry the cold or the right signals, while Sleeve carries the grounding signal.