This is actually two charming early 14th-century buildings facing each other (sort of like the al-Ghuri mosque-mausoleum complex near al-Azhar) on the street leading from the Sultan Hassan mosque to the Ibn Tulun Mosque. As a result, it's a nice location to admire on a walk between those two more impressive mosques. The mosque is on the north side of the street while the khanqah (a religious space and lodge for sufis/Muslim mystics) is on the south side.
If you're interested in Cairo's medieval (Mamluk) architecture, then they're worth a closer look. Although the two buildings look identical at first sight, they're actually different in many ways. The two minarets seem to be identical, however, and the visual effect of having them frame the street on both sides (almost like goal posts!) is clearly deliberate, and demonstrates how medieval builders were trying to dominate the skyline along certain important avenues in Cairo.
One interesting detail to notice on the outside of the khanqah is the pharaonic block above the doorway. The inside of that building, to my knowledge, is not open for visitors (or at least I've never seen it open). I don't think it's being used for anything currently.
The mosque, however, opens for prayer times only; you can usually have a look inside just after prayers finish, before the imam closes it up again. There are some lovely painted ceilings and other interesting details, including some excavations of a cistern (apparently) at the back. If you're only visiting the highlights of Islamic Cairo, though, it may not be worth going out of your way.