By Josh Beckerman
Shares of medical device company Zynex Inc. rose 8% to $23.05 after hours as the company was selected to join the S&P SmallCap 600 index.
S&P Dow Jones Indices said Zynex will replace Kemet Corp. next Tuesday, before trading opens. Kemet is being sold to Yageo Corp.
Zynex said in April that first-quarter revenue rose 66% to $15.2 million.
Write to Josh Beckerman at josh.beckerman@wsj.com