 HOUSTON--BUSINESS WIRE--PROS NYSE: PRO, a provider of SaaS solutions optimizing shopping and selling experiences, today announced updated fourth quarter and full year 2021 guidance and the fourth quarter and full year 2021 financial results release date. Fourth Quarter and Full Year 2021 Financial Outlook PROS currently anticipates the following based on an estimated 44.4 million basic weighted average shares outstanding for the fourth quarter of 2021 and a 22 non-GAAP estimated tax rate 