Having done a fair bit of research I chose the Naenka runner pro headphones to use for swimming. The headphones arrived promptly in good looking packaging. The Bluetooth playback works well but the internal mp3 usb flash drive is not accessible. I have emailed Naenka three times in the last week and have not had any response. There is no contact options on their website and I now realise this is a Chinese supplier with worldwide fulfilment. Very disappointing and if I do not hear from Naenka soon I will be seeking a refund from PayPal or mastecard.