That's a Lian Li V-1000 series, and the wheels come with them. They are milled from solid aluminum.
If you really like them, you can buy a set here: Lian Li Solid Aluminum Casters [WB-01] : Performance-PCs.com, ... sleeve it and they will come
If you really like them, you can buy a set here: Lian Li Solid Aluminum Casters [WB-01] : Performance-PCs.com, ... sleeve it and they will come