The unit of radius distance in proximity (for example, MILES)

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v26/enums/proximity_radius_units.proto)

| Enums ||
|---|---|
| ## `KILOMETERS` | Kilometers |
| ## `MILES` | Miles |
| ## `UNKNOWN` | Used for return value only. Represents value unknown in this version. |
| ## `UNSPECIFIED` | Not specified. |