# Meter

> The meters optional block of a .well file: a list of Meter objects.

Property `meters` of the .well root, an array of objects, optional. [Defined in the spec](/format/spec/v2/object-schemas#meter).

| Field | Type | Required | Values / constraints | Description |
| --- | --- | --- | --- | --- |
| `id` | string | yes |  |  |
| `installed_at` | string | yes | pattern `^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?(Z\|[+-]\d{2}:\d{2})$` |  |
| `removed_at` | string | no | pattern `^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?(Z\|[+-]\d{2}:\d{2})$` |  |
| `installed_by` | string | no |  |  |
| `removed_by` | string | no |  |  |
| `type` | string | no |  |  |
| `manufacturer` | string | no |  |  |
| `model` | string | no |  |  |
| `serial` | string | no |  |  |
| `nominal_diameter` | number | no | >= 0 |  |
| `max_reading` | number | no | > 0 |  |
| `notes` | string | no |  |  |
| `updated_at` | string | no | pattern `^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?(Z\|[+-]\d{2}:\d{2})$` |  |
| `attachments` | [Attachment](/format/reference/objects/attachment)[] | no |  |  |