http://www.pcgamer.com/rainbow-six-siege-is-free-to-play-this-weekend-season-four-update-testing-to-follow/

Ubisoft's team-based shooter Rainbow Six Siege is going free to play for the weekend, and if you like what you see you'll also be able to pick up the full game for half price. 

The free-play weekend will begin 9 am PT/12 pm ET on November 16 and run until 12 pm PT/3 pm ET on November 19, while the sale price will actually hold for an extra day, until 9 am PT/12 pm ET on November 20. Preloading is live now, so you don't have to waste any of that precious free time, and if you elect to make the purchase, any progress earned during the freebie will carry over.