What is this gray part?

[BrunoShady]

Anybody have an idea what it does?
Can I take it out without damage the phone?

It seems some kind of rubber or flexibel metal

 

[montsa007]

It helps your phone take power from a charging mat.
Not sure if it is safe to remove it.

 

[Muessig]

The gray part is the adhesive, sticking the wireless charging coil to the rear cover of your phone.

 

[gwinegarden]

Why would you want to? Most times it's best to leave well enough alone.

 

[WanderingTraveler]

Why would you want to? Most times it's best to leave well enough alone.

Maybe he's one of the people who, I don't know, prefer lighter phones?

 

[Jason Drum]

Heat sink?

 

[montsa007]

Maybe he's one of the people who, I don't know, prefer lighter phones?

That thing doesn't weigh a done besides removing that could rattle things inside the phone, leave some sticky substance and get your phone killed!