Bodo Ruthenberg, Wet's founder and chairman of the supervisory board, holds the majority of the shares. Hg Capital has offered to buy approximately 65 percent of his holding for 100 million euros. Hg Capital plans to make a takeover offer to the remaining shareholders at an equivalent rate, which equates to 52.70 euros per share.
Wet was formerly listed on Germany's defunct Neuer Markt.
"It is the aim of the investor to buy at least 95 percent of the total shares," said Wet financial director Dieter Haap.
Trevor Bayley, head of Hg Capital's German office, said if the takeover is successful the private equity group would look at a number of acquisitions to strengthen Wet's business.