This is a simple 3.5mm TRS stereo audio jack with a screw-on plastic shroud. These are great for projects that plug into headphone jacks. Stereo plugs can
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Audio Plug - 3.5mm - COM-11143 - SparkFun Electronics
These are great for projects that plug into headphone jacks. Stereo plugs can also be used for carrying serial comm connections!
[ SparkFun COM-11143 ] Audio Plug - 3.5mm (1/8)
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Audio Plug - 3.5mm - COM-11143 - SparkFun Electronics
Audio Plug, 3.5mm, TRS Stereo Connector - Proto-PIC