Led by Trump-appointed Chairman Ajit Pai, the FCC is set to vote tomorrow on a proposal to roll back net neutrality protections. Ahead of that vote, a group of Senate Democrats have published an open letter in TechCrunch defending the rules.

“These rules protect the internet as an open, decentralized, and level playing field, free from content discrimination,” the letter, titled “An open letter to everyone who uses the internet,” reads. “They ensure that you—not your internet service provider (usually your cable or phone company)—control what you can access online.”

The letter — signed by 13 senators, including Elizabeth Warren, Cory Booker, Kamala Harris, and Chuck Schumer — lists three problems that could be caused by the rollback: internet service providers could create preferred content “fast lanes,” they could limit access to only select websites, and they could block access to some services. Similar bullet points have been the nightmare scenarios for net neutrality advocates.

“This does not have to be the future of our internet,” the letter reads. “We know what it’s going to take to protect net neutrality. We’ve won on this before. We can win again. And you will be hearing us speak out on this issue in the Senate and in every corner of the country.”

The letter ends by encouraging dissent against the changes. “The existing net neutrality rules protect this foundation and the connected society that we all enjoy. Don’t let the FCC take that away.”