There are two known $\mathrm{GQ}(9,9)$s, namely $\mathrm{O_5}(9)$ and $\mathrm{Sp}_4(9)$. Each one is the dual of the other.
| Number of vertices: | $820$ |
| Diameter: | $2$ |
| Intersection array: | $\{90,81;1,10\}$ |
| Spectrum: | $90^1 8^{450} (-10)^{369}$ |
| Automorphism group: | $\mathrm{PS_p}(4,9):2$ |
| Distance-transitive: | Yes |
| Primitive |