This week, these five stocks have the best ratings in Operating Margin Growth, one of the eight Fundamental Categories on Portfolio Grader.

United Fire Group (NASDAQ: UFCS) writes property, casualty, and life insurances. UFCS also gets A’s in Earnings Momentum, Analyst Earnings Revisions, and Earnings Surprises. Shares of the company are up 24.8% from the first of the year, better than the Nasdaq’s 22.1% increase over the same period. For more information, get Portfolio Grader’s complete analysis of UFCS stock.

Western Alliance Bancorp. (NYSE: WAL) provides a range of banking and related services to businesses, professional firms, real estate developers and investors, local nonprofit organizations, high net worth individuals, and consumers. WAL also gets A’s in Earnings Growth and Analyst Earnings Revisions. Shares of the stock have risen 66.1% since January 1. For more information, get Portfolio Grader’s complete analysis of WAL stock.

Symmetricom (NASDAQ: SYMM) generates, distributes and applies precise time for the communications, aerospace/defense, IT infrastructure and metrology industries. SYMM also gets an A in Earnings Surprises. The price of SYMM increased 26.9% from January 1. For more information, get Portfolio Grader’s complete analysis of SYMM stock.

Mellanox Technologies (NASDAQ: MLNX) designs and develops semiconductor-based, high-performance interconnect products. MLNX gets A’s in Earnings Growth, Earnings Momentum, Analyst Earnings Revisions, Earnings Surprises, and Sales Growth as well. The price of MLNX is up 241.7% since the first of the year. For more information, get Portfolio Grader’s complete analysis of MLNX stock.

Cray (NASDAQ: CRAY) designs, develops, manufactures, markets and services high performance computing systems, commonly known as supercomputers. CRAY gets A’s in Earnings Momentum, Analyst Earnings Revisions, Earnings Surprises, Equity, Cash Flow, and Sales Growth as well. Since January 1, CRAY has jumped 108.2%. The stock has a trailing PE Ratio of 2.9. For more information, get Portfolio Grader’s complete analysis of CRAY stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.