 The newest and most advanced version of the Su-27 is the Su-35S ("Serial").The Su-35 was previously referred to as the "Su-27M", "Su-27SM2", and "Su-35BM".The Su-37 is an advanced technology demonstrator derived from Su-35 prototypes, featuring thrust vectoring nozzles made of titanium rather than steel and an updated airframe containing a high proportion of carbon-fibre and Al-Li alloy.