What scope applies to Custom Metrics?

Each time the tracking code is triggered by a user’s behavior (for example, user loads a page on a website or a screen in a mobile app), Analytics records that activity. Each interaction is packaged into a hit and sent to Google’s servers. Similar to custom dimensions, custom metrics can have different scopes. Hit-level custom metrics get associated with all the hit level dimensions with which it was sent. Similarly, product-level custom metrics are associated only with the product with which it was sent. Tip: Custom metrics can produce more flexible and more readable custom reports and as such are a convenient way to track your most important metrics.