Every day, TheStreet.com Ratings compiles a list of the top 10 stocks in five categories -- fast-growth, all-around value, large-cap, mid-cap and small-cap -- and publishes these lists in the Ratings section of our Web site. The top 10 rankings are based on our ratings, which assess risk-adjusted returns as well as other criteria specific to the type of stock. We update the lists at the end of the business day on the basis of information available at the close of the previous trading session. Beginning with this week, we are publishing a daily article that takes a closer look at the ratings of the stocks on one of the lists. Today we'll look at mid-cap stocks. These are stocks with a market capitalization of between $500 million and $10 billion that rate near the top of TheStreet.com Ratings' coverage universe. In addition, the stocks must be followed by at least one financial analyst who posts earnings estimates on IBES. The stocks are ranked in the order of their potential to appreciate. Hub Group ( HUBG), a full-service transportation provider, offering intermodal, truck brokerage and logistics services throughout North America, has been rated buy since December 2004. The company's strengths include its notable return on equity, revenue growth, largely solid financial position with reasonable debt levels by most measures, impressive record of earnings-per-share growth and compelling growth in net income. TheStreet.com Ratings believes these strengths outweigh the fact that the company shows low profit margins.