Elon Musk is all in on Twitter, offering roughly $43 billion to buy out the public company and take it private. The world’s richest man already owns 9.2% of Twitter and is the company’s largest shareholder.

According to an SEC filing, Musk would pay $54.20 per share, which is an 18% premium over Wednesday’s share price and a 38% premium over the share price of the company the day before Musk’s 9.2% stake became public.

I made an offer https://t.co/VvreuPMeLu

— Elon Musk (@elonmusk) April 14, 2022

In a notice to Twitter board chairman Bret Taylor, Musk wrote that the offer “is my best and final offer and if it is not accepted, I would need to reconsider my position as a shareholder.”

The buyout proposal comes after Musk declined a seat on the board this past week, which was offered to him after he bought 9.2% of the company and declared interest in influencing operations. The appointed board seat would have prevented Musk from owning more than 14.9% of the company. He rejected the seat the morning his appointment was to take effect.

“I invested in Twitter as I believe in its potential to be the platform for free speech around the globe, and I believe free speech is a societal imperative for a functioning democracy,” Musk told Taylor. “However, since making my investment I now realize the company will neither thrive nor serve this societal imperative in its current form. Twitter needs to be transformed as a private company.”

Musk’s over-value offer is what’s known as a bear hug, where a company or person offers to buy the shares of a target company at a price much higher than what it is worth on the market. Because the targeted company–in this case Twitter–is obligated to do what’s in the best interest of shareholders, it makes it difficult for management to reject the offer.

At roughly $43 billion dollars, the amount Musk is offering is about 16% of his personal net worth.