The box itself is a 5.25inch CD-drive case so you can mount it into standard ATX PC cases.
It was over 2 hours work to create this from a used CD drive and bitumen sheets.
The sheets cost over 20 EUR, so the starting price of 45 EUR is very cheap.
As far as I remember, bitumen is a good heat-conductor so the harddisks will not heat up too much.
Its noise damping property is also good
The bitumen sheets which were used are special sheets for being used in such things so they do not stink like the bitumen you know from streets does.
Notice that I offer a second one in my other auctions.
https://www.bitmit.net/de/trade/i/4483-handcrafted-bitumen-harddisk-noise-attenuation-box/description
https://www.bitmit.net/de/img/trade_uploads/2012/07/26/handcrafted-bitumen-hardd_8eefb_1.jpg