By Chris Wack 



  21Vianet Group Inc. shares hit their 52-week high of $22 after the company said funds managed by Blackstone have agreed to make a $150 million investment in the company. 


  Following the investment, Blackstone will become one of 21Vianet's largest institutional stockholders. 


  The company's stock was recently up 11% to $20.32 on volume of 3.3 million shares. Its 65-day average volume is 945,000 shares. 


  21Vianet said the investment will strengthen its balance sheet and help support the rapid growth that it is experiencing in wholesale and enterprise data center markets. 21Vianet intends to use the proceeds from the private placement on capital expenditures to reinforce its position in China's hyper growth data center market. 


  The investors will subscribe $150 million newly issued series A perpetual preferred shares, which are convertible into American Depositary Shares at a conversion price of $17 an ADS. 


  As part of the transaction, Blackstone will designate a non-voting observer to attend meetings of the 21Vianet board, subject to maintaining its shareholding at or above a specified percentage threshold. 


  Write to Chris Wack at chris.wack@wsj.com