Each weekday, 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 on 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. The following day, we publish an 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 market capitalization 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 the Institutional Brokers' Estimate System. The stocks are ranked in the order of their potential to appreciate. Leading off this week's list is Gorman-Rupp ( GRC), which designs, makes and sells pumps and related equipment for use in construction, industrial, petroleum, agricultural, fire and military applications. It has been rated a buy since November 2005. The company's gross profit margin for the third quarter of its fiscal year 2006 increased from the same period a year earlier. During the same quarter, Gorman managed to increase sales (20.09%) and net income (147.2%) at a faster pace than the average competitor in its industry. The company is also extremely liquid, and it increased its liquidity in the third quarter, indicating improved cash flow.