Purpose of Flanker and Fullback Rear Protrusion?

[OnNom]

What is the purpose of the large protrusion past the back of the plane on the Flanker and Fullback?

 

Is it for some aerodynamic purpose?

 

I don't see this too much on other planes, not even on the MiG-29 which has a similarly shaped air frame.

Edited August 6, 2020 by OnNom

[Fri13]

One Su-27 had a rear radar there. But standard is to have a landing chute there.

But something there could be for aerodynamic use as those are so long, real stingers really.

[AeriaGloria]

Contrary to popular belief the Su-34 has an APU back there

[Fri13]

Contrary to popular belief the Su-34 has an APU back there

 

That can be seen here in Su-34, similar to others:

 

 

I always remember that APU was like 1-2 meters toward nose, more between the engines.

It is just crazy how long and big those "stingers" really are. But to have a APU, ECM and Chute inside there, it just takes lots of space and allows to keep very nice streamlined body.