The Music Store 3.5mm Mini Jack To 6.5mm Stereo Jack Adapter is ideal for use with headphones for converting a mini jack to a 1/4" jack plug.
Its a simple and portable 3,5mm to 6,5mm adaptor.
I had no trouble with it whatsoever, it works fine.
I use it on my Yamaha PSR E-343 keyboard because the plug is 6,5mm. Now I can "not disturb" others with my playing.