Rivian Automotive Inc (Rivian (RIVN)) shares are taking a hit in extended trading Monday after the electric vehicle maker announced a public offering. The stock was down nearly 8% after hours, trading at $18.55 at the time of publication.

Here's the deal: Rivian is offering up to 75 million shares of common stock in an underwritten public offering. On top of that, the company is giving underwriters a 30-day window to buy up to an additional 11.25 million shares at the offering price, which hasn't been disclosed yet. All the shares are being sold by Rivian itself, so the proceeds will go straight to the company's coffers.

What's Rivian planning to do with all that cash? The company says it will use the net proceeds for general corporate purposes, including funding certain equity contributions under an Amended and Restated Loan Arrangement with the U.S. Department of Energy. As of the end of the first quarter, Rivian had about $4.83 billion in cash, cash equivalents, and short-term investments.

Investors aren't thrilled about the dilution, and the after-hours price action reflects that. Rivian shares were down 7.89% in Monday's extended session.