When Robinhood was raising its early funding rounds, co-founder Baiju Bhatt kept a journal. In it were pages filled with the names of over 100 investors, most of them accompanied by an “X” mark to indicate they had passed on the investment, said an early investor who saw the journal.

Those who were less skeptical of a commission-free mobile app for stock trading are in for a big payday now. Venture firms Index Ventures, Ribbit Capital, NEA and DST Global in particular are expecting big gains when Robinhood completes its long-awaited initial public offering, likely later this month.

The Information has gathered the expected returns for these firms and Robinhood other’s major backers, including early-stage firms Elefund and Susa Ventures, as well as those such as Sequoia Capital that flocked to the app when it became popular years later.