I have a Camelbak Octane XCT that I used to use for long runs. Holds up to 3 litres, which is more than I've ever needed. Very comfortable, with additional little pockets for things, like phone, sunglasses, gels, gloves, rain jacket. Also exceptionally useful when filled up with ice, made running around Skiathos in the height of summer bearable. It was useful for any runs over an hour, as that's how long 500ml in my water bottle lasts. Though I really like my water bottle because that just straps to my hand. Nike don't appear to make it anymore, and all the others I've seen are much bulkier.