> [!CAUTION]
> **Caution:** This documentation is for Google Ads API **v24** . The latest active version is [**v26**](https://developers.google.com/google-ads/api/reference/rpc/latest/FrequencyCapKey).

A group of fields used as keys for a frequency cap. There can be no more than one frequency cap with the same key.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v24/common/frequency_cap.proto)

| Fields ||
|---|---|
| ## `event_type` | `FrequencyCapEventType` The type of event that the cap applies to (for example, impression). |
| ## `level` | `FrequencyCapLevel` The level on which the cap is to be applied (for example, ad group ad, ad group). The cap is applied to all the entities of this level. |
| ## `time_length` | `int32` Number of time units the cap lasts. |
| ## `time_unit` | `FrequencyCapTimeUnit` Unit of time the cap is defined at (for example, day, week). |