Each weekday, TheStreet.com Ratings compiles a list of the top five 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.

This list, updated daily, is based on data from the close of the previous trading session. Today, mid-cap stocks are in the spotlight. These are stocks of companies that have market capitalizations of between $500 million and $10 billion that rank near the top of all stocks rated by our proprietary quantitative model, which looks at more than 60 factors.

The stocks must also be followed by at least one financial analyst who posts estimates on the Institutional Brokers' Estimate System. They are ordered by their potential to appreciate.

Note that no provision is made for off-balance-sheet assets such as unrealized appreciation/depreciation of investments, market value of real estate or contingent liabilities that might affect book value. This could be material for some companies with large underfunded pension plans.

Manitowoc ( MTW - Get Report) manufactures and markets cranes and related products, food service equipment and marine products. The company demonstrates notable revenue growth, significant EPS improvement, impressive stock price appreciation and net income growth that has significantly outpaced that of the S&P 500 and its industry.

Its price level is now somewhat expensive compared with the rest of its industry, but given its strengths, the higher price is justified. Manitowoc's low profit margins are not a threat to its buy rating at this time.

Oneok Partners ( OKS) has maintained a buy rating since June 2006. The company has recently acquired valuable natural gas and processing assets that reduce its dependence on regulated, fee-based transportation revenue. Oneok shows impressive revenue growth and return on equity that is significantly higher than the industry average. It also has enjoyed notable net income growth.

Risks to the buy rating include an unexpected rise in interest rates, which could drag down profits because the company has taken on more debt to fund its aggressive expansion strategy. Oneok is also vulnerable to the risk of a compressed gathering and processing margin, which is related to volatile natural gas prices.

Greif ( GEF - Get Report), which makes industrial packaging products, has secured a buy rating since December 2004. Greif shows a convergence of positive investment measures, including a notable return on equity, revenue growth that has outpaced its industry, and compelling growth in net income.

In June, the company said second-quarter revenue grew to $815 million from $620.1 million. Greif also increased its fiscal 2007 earnings outlook, excluding items, to between $3.05 and $3.10 a share. The company has demonstrated a pattern of positive EPS growth over the past two years. However, we anticipate this pattern will end in the coming year.

Triumph Group ( TGI - Get Report), an aircraft-components company, has maintained a buy rating since August 2005. The company has demonstrated impressive growth in revenue, net income and earnings per share, along with good cash flow from operations.

In May, Triumph Group said its annual net income for fiscal 2007 increased 36% to $47.1 million, or $2.87 a share. Annual sales totaled $954.7 million, up from 26% from a year ago. These factors should outweigh the company's low profit margins.

Natco Group ( NTG - Get Report), which makes oil and gas production equipment, has been rated buy since November 2005. The company has shown robust top-line and bottom-line growth, margin expansion, notable EPS growth, and an improved short-term liquidity position. For the first quarter of 2007, Natco said revenue increased 8% to $127.4 million. Net income for the quarter totaled $8.4 million, or 45 cents a share, up from $7.5 million, or 41 cents a share, a year ago.

Natco is experiencing a slowdown in certain businesses, including a lower use of resources in the Gulf of Mexico, delays in built-to-order project awards, and a decline in booking. Looking ahead, the company's performance will depend on sustained strength in its key markets.