Small balls in HDD

Today I've opened my old hard drive, just for fun. And something very interested me. On the upper case I've seen a glued, small box with a hundreds of very small balls. I was trying to find something about it, but nothing. Magnet doesn't effect on they. So they aren't ferromagnetics. I don't know if it is even metal.

Anybody knows, what the hell is this?

 

Sorry about post under post, but I've taken photos:

http://img247.imageshack.us/img247/1203/dsc00684lv8.th.jpg

http://img247.imageshack.us/img247/2623/dsc00683uw2.th.jpg

Box is opened by me, so many balls fell out.

 

They are ball bearings, like on a motor etc. and they are non-magnetic because that's how the tracks on the platter are written, I assume that ferrous material could cause interference. There must be a wiki etc. on that.

 

maybe to balance/counter balance something in there?

 

As a guess their as "dampners", to absorb the drive activity and minimise the head from skipping and or moving. They minimise the head "skipping", like playing a vinyl record and having people jump, they absorb the "inflection".

 

Do you mean that, vibrations or shakes are take by these balls?

 

Well Im just guessing that they absorb vibration.

 

I think they are "moisture absorbers", similar to silica gel packs you find in many products.