6.3mm mono plug to 3.5mm mono jack FEV-B121By gerry / February 21, 2021 6.3mm mono plug to 3.5mm mono jack FEV-B121A. 6.3mm mono plug to 3.5mm mono jack;B. 6.3mm mono plug to 3.5mm stereo jack (assembled type)A. 6.3mm mono plug to 3.5mm mono jack; B. 6.3mm mono plug to 3.5mm stereo jack (assembled type)