** Shares of EV maker Rivian RIVN.O down 8% at $18.50 in extended trading

** RIVN says it will offer 75 million shares to raise capital

** Adds offering could expand further, with RIVN granting the underwriters a 30-day option to purchase up to an additional 11.25 million shares

** Co intends to use the net proceeds for general corporate purposes, including funding equity contributions required by its amended and restated loan arrangement and reimbursement and sponsor support agreement with the U.S. Department of Energy

** Co also expects revenue between $1.55 billion and $1.65 billion in Q2, compared with $1.30 billion it reported a year earlier

** As of last close, stock up ~2% this year