As a keen long distance runner I like to listen to music when running. The problem I have always had is that sweat invariably causes my headphones to malfunction (as I sweat quite a bit). I have tried all sorts that claim to be 'sweat-proof' and yet I always end up with music only in one ear or with gradual decreasing volume. Additionally, for a 6'1 bloke, I have very small ears and found it very difficult to find headphones that would stay in my ears comfortably while I ran. 'In your ear' products would fall out while most clip-on/over-ear designs seem to be one size fits all and that one size seems to be Prince Charles or the BFG! So, I wanted headphones that didn't react badly to sweat and fitted my small ears comfortably. I initially tried a Sony clip on type, which actually fitted my ears but despite claiming to be water/sweat resistant often lost sound in one ear in less than 30 minutes. So I tried the MDR-AS30G. They fit quite loosely in the ear and are padded so I found them perfectly comfortable and I have never had sore ears. They were stable due to the neck band and the sound was good. Most importantly, I have never experienced any loss of quality from sweat even when running a half marathon. The only possible down side could be that they drown outside noise a bit too well, making it potentially hazardous if you run on main roads. But all in all they do what I wanted them to for a very good price.