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# Factorio Runtime Docs Version 2.0.7

## SurfaceIdentification :: union

A surface may be specified in one of three ways.

#### Union members

uint | It will be the index of the surface. `nauvis` has index `1`, the first surface-created surface will have index `2` and so on.
string | It will be the surface name. E.g. `"nauvis"`.
LuaSurface | A reference to LuaSurface may be passed directly.