Shares of Herc Holdings Inc. (HRI) plummeted 9.52% in pre-market trading on Tuesday, following news that the equipment rental company has made a bid to acquire H&E Equipment Services (HEES).

According to reports, H&E Equipment has received a "superior proposal" from Herc Holdings to acquire all of its outstanding common stock. While financial details of the offer were not disclosed, the proposed acquisition has raised concerns among investors about the potential risks and costs associated with integrating the two companies.

Large acquisitions often put downward pressure on the acquirer's stock price, as investors weigh the potential benefits against the challenges of combining operations and integrating corporate cultures. Some analysts may also question whether the deal creates sufficient value for Herc Holdings' shareholders, particularly if the purchase price is viewed as too high.