> [!CAUTION]
> **Caution:** This documentation is for Google Ads API **v23** . The latest active version is [**v26**](https://developers.google.com/google-ads/api/reference/rpc/latest/FlexibleRuleOperandInfo).

Flexible rule that wraps the common rule and a lookback window.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v23/common/user_lists.proto)

| Fields ||
|---|---|
| ## `lookback_window_days` | `int64` Lookback window for this rule in days. From now until X days ago. |
| ## `rule` | `UserListRuleInfo` List of rule item groups that defines this rule. Rule item groups are grouped together. |