The grades of three medical devices stocks are on the rise this week on Portfolio Grader. Each of these stocks is rated an “A” (“strong buy”) or “B” overall (“buy”).

Winner Medical Group (WWIN) is making headway this week, with the company’s rating improving to an A (“strong buy”) from a B (“buy”) last week. Winner Medical Group engages in the research, development, manufacture, and marketing of cotton-base medical dressings and medical disposables. For more information, get Portfolio Grader’s complete analysis of WWIN stock.

Antares Pharma, Inc. (ATRS) is bettering its rating of C (“hold”) from last week to a B (“buy”) this week. Antares Pharma develops pharmaceutical delivery systems, including needle-free and mini-needle injector systems and transdermal gel technologies. Shares of the stock have been changing hands at an unusually rapid pace, twice the rate of the week prior. For more information, get Portfolio Grader’s complete analysis of ATRS stock.

Medtronic, Inc. (MDT) gets a higher grade this week, advancing from a C last week to a B. Medtronic develops therapeutic and diagnostic medical products. The stock has pushed up 3.9% over the past week. For more information, get Portfolio Grader’s complete analysis of MDT 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.