I buy it in 1 lb bags at work quite frequently, and my best friend will go right to spinrite to get it... it's the ends of a mill run of yarn. Any factory will deliberately make an over-run of the product they produce. That way any errors or poor quality items can be removed from the production run, and there will still be enough left to fill the order. The amount left-over from a mill run of yarn will be sold as mill ends... usually by the ounce or by the pound. It's frequently a great way to get some excellent yarn at a deeply discounted price --- just ask anyone that goes to Spinrite in August!