It uses SE fast port connector. I have them for my k750 and although a 3.5mm jack on the phone would be ideal you can use whatever headphone you want as there is a spot on the mic to switch them.
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No standard 3.5mm jack. It will use [and probably come with] something like this http://rex_zw.nease.net/lofty-eb/goodsimage/1122/hpm-70.gif
It uses SE fast port connector. I have them for my k750 and although a 3.5mm jack on the phone would be ideal you can use whatever headphone you want as there is a spot on the mic to switch them.