The largest initial public offering ever is just days away, and demand for SpaceX stock is expected to be extremely high, with Wall Street clamoring to buy Elon Musk’s rocket and satellite company.

The flip side of all that buying is plenty of selling as investors need to raise cash for stock purchases by liquidating other shares in their portfolios.

To be sure, IPOs are often accompanied by volatility. But Greg Boutle, head of U.S. equity derivative strategy at BNP Paribas, pointed out in a note Friday that what’s different this time is SpaceX-related volatility will be coupled with the largest market cap ever seen in a U.S. IPO.

SpaceX plans to raise at least $75 billion in its IPO by selling over 555 million…