The biggest venture capital shareholders in messaging firm Slack stand to make billions of dollars when the company goes public on Thursday. One of the big questions surrounding the listing is how fast the VCs, who as a group own a majority of the stock, will want to lock in those gains by selling their shares.

Unlike a conventional initial public offering, Slack is hitting the public markets through a direct listing, in which no money is raised and investors don’t have to wait months for the end of a traditional lockup period on their shares. That could add to selling pressure in the first few weeks. The market’s other recent, high-profile company to go public through a direct listing, Spotify, did so with a more diverse set of investors who might be more likely to hold shares for a long period on the public markets.