I measured a frame I already had and fit comfortably, then looked for frames of similar size. On sites like Zenni and 39dollarglasses, the frames are categorized by material and shape, then by size - temple width, arm length being two. Look here 39dollarglasses.com -- Help Topics - How do I measure the frame I already have?For those of you who purchase your glasses online, how do you get them adjusted to fit comfortably? How do you determine if the frames are the right size for you (eye to eye and temple length?)