This week, four commercial services stocks are improving their overall rating on Portfolio Grader. Each of these rates an “A” (“strong buy”) or “B” overall (“buy”).

Republic Services, Inc. (RSG) is progressing from last week’s rating of B (“buy”) as the company improves to an A (“strong buy”) this week. Republic Services provides non-hazardous solid waste collection services for commercial, industrial, municipal and residential customers. In Portfolio Grader’s specific subcategory of Margin Growth, RSG also gets an A. For more information, get Portfolio Grader’s complete analysis of RSG stock.

This week, Viad Corp (VVI) is showing significant improvement as the company’s rating hops from a C (“hold”) to a B (“buy”). Viad provides high-quality, place-based marketing services in North America, the United Kingdom and the United Arab Emirates, as well as travel and recreation services in the United States and Canada. For more information, get Portfolio Grader’s complete analysis of VVI stock.

This is a strong week for Hudson Technologies, Inc. (HDSN). The company’s rating climbs to B from the previous week’s C. Hudson Technologies sells refrigerants, as well as provides a variety of related services. Shares of the stock have been trading at an exceptionally rapid pace, up twofold from the week prior. For more information, get Portfolio Grader’s complete analysis of HDSN stock.

This week, Waste Management, Inc.’s (WM) ratings are up from a B last week to an A. Waste Management provides collection, transfer, recycling, disposal and waste-to-energy services. For more information, get Portfolio Grader’s complete analysis of WM 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.