A new medium size/medium range supersonic stealth fighter bomber concept (JH-21? Project 176?) was studied at the 601 Institute in the 2000s. It appeared to feature a twin seat cockpit and twin engines. A mock-up (head section?) was constructed at SAC during 2013. The design was rumored to have been transferred to 603/XAC to be further developed into a medium stealth bomber. The current status of this project is unknown.