Any way, the original O11 is mainly alu. BUT however it is made of steel inside.
If you all noticed the new pc37 o11 o12 series all are made half steel half alu.
Hence the price is slightly lower than most of their other full alu towers. However it is still on a high side such as paying 4xx to 6xx for it.
The original o11 have all alu for both the side and front panel. The mobo tray is alu.
The things that are steel was the case structure, pcie brackets and the hdd cage.
This new o11 dynamic is all steel material. A redesign on the inside. Accepting a proper 2x 360mm rads with push pull and also bottom rads. Making it the smallest case to fit in a lot of rads and yet without compromising cable management space at the 2nd chamber.