Andrew Left is bullish on shares of Twitter at its current price level.

Twitter is “a compelling product,” Left said in an interview on CNBC’s “Halftime Report” Friday. “When you compare the market cap to Facebook, it has a long way to go. … It’s a compelling platform for where its trading.”

Twitter has a market value of nearly $18 billion midday Friday versus Facebook’s $547 billion market cap.

Tweet Link

The well known short-seller revealed on his firm’s social media account he is long Twitter shares. The investor said Twitter’s competitive position in the social media space is underrated.

“You can see the engagement levels on Twitter and the relevancy its playing in our society can’t be denied,” he said. “They dominate that space of social media.”

Greenlight Capital’s David Einhorn also revealed his fund bought Twitter shares on Jan. 16 in a note to investors.

“Despite a massive user base and broad reach, Twitter has an enterprise value of about 2% of Facebook, the largest social media platform,” Einhorn wrote.

Left gained notoriety for successful bets against stocks such as Valeant Pharmaceuticals. He is known for his bearish company-specific reports published his website Citron Research.

Shares of Twitter are up 8 percent Friday.