The Sony NWWS413 is a 4GB MP3 player built into a set of waterproof and dust-proof IP67/68 headphones. The Sony Walkman NW-WS413 headphones are comfortable and a good fit would be an understatement. While they might look bulkier than your usual in-ears, they certainly don’t feel it. They’re light and well fitted so that whether you’re running or swimming they sit perfectly in place throughout. The type of waterproofing is a factor, too.Sony has upgraded this generation to not only be waterproof but resilient in salt water for up to 2m for 30 minutes as well as being sand and dust proof. This means the Sony Walkman should be able to remain on your ears pretty much anywhere you go.