Does somebody knows what kind of material is ?

[Nacho-RT74]

the stuff what fills and seals the back of ECU modules ?

[440]

Probably an electronic potting epoxy, should be able to get it at any good electronics shop.

[Nacho-RT74]

it looks kinda a silicone/rubber... aren't epoxy stuff more "solid" ?

[DC_1]

it looks kinda a silicone/rubber... aren't epoxy stuff more "solid" ?

In the electronics field they are alled potting compounds. They can be rigid or like rubber/silicone depending on the application. They have conductive, non-conductive, high temp, low temp, clear to coloured, hard compound to soft, all depends on what you want to achieve.

Here are a few

http://www.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=Potting+compound

[Nacho-RT74]

IIII LIKE THAT!

the original looks to have somekind of sand stuff

[seaweed]

I belive that "the sand" is Silica gel, to draw the moist from the circuit.

[Nacho-RT74]

mmmmmm... sounds kinda logic