EOS 550D What is this piece?

[Atheer]

I removed the lens to clean the sensor and this piece fell of. I do not know if it fell from the lens or sensor 

My camera is Canon 550D

[MikeSowsun]

Many consumer lenses are open at the back and it's not uncommon for broken parts to fall out. 

[Tronhard]

Mike that is a huge chunk of hardware to come out of the back element of a lens!  I have found a site that might be better able to answer this question: Here .

[MikeSowsun]

That piece may be big, but so is the opening around the rear element on these consumer lenses. 

Here us a video showing disassembly of an 18-55. That part is called the "focusing brush" and can be seen at 9:40 in this video. 

https://youtu.be/xrKbuLHeifw

[Tronhard]

Wow... You appear to be spot on.  It's much smaller than I thought, even given the image of the OP's hand.  Well, one wonders how that came adrift!   I would suspect it might be cheaper to get a replacement 18-55 (this time an STM version) than to have the lens disassembled and fixed.  Given this has come out, I would guess the lens has had a serious knock at some stage, so the optics might be out too.

[MikeSowsun]

That brush in the original post doesn't look like it came from an 18-55.  I'd be curious to know what lens or lenses the OP has. 

Here are more examples of "brushes".