One HDD frame can be removed so that even the longest graphics cards have room. The HDD frames are visible in the last picture (no. 6). The lower HDD frame can remain in place, so there is still room for 3 hard disks.
I had installed an ATI Radeon HD 6950 and a Radeon HD 7970 - one after the other. But they would also fit next to each other. At 27 cm, the 7970 is not the longest available, but there is still about 10 cm of space in the case.