With adaptive banners, a portion of inventory can accommodate flexible ad sizes.
To compete for this inventory, your integration must interpret the multi-size
fields in the bid request.

By interpreting multi-size bid requests, you can do the following:

- **Access more inventory:** Bid on a larger pool of impressions from users adopting adaptive banners.
- **Increase win rate:** By considering a wider size range of eligible banner ads for flexible ad slots, you can submit competitive bids to increase bid rate.

This guide covers supporting multi-size bid requests.

## Read multi-size requests

To bid on adaptive banner inventory, you must do *either* of the
following:

- Read the `BidRequest.imp.banner.format` array. This array contains:
  - The requested size, which might be non-IAB standard.
  - IAB-standard sizes that are smaller than the requested size.
- Read the minimum and maximum width and height from the `BidRequest.imp.banner.ext.flexslot` extension. This Google-specific extension provides information about the full range of accepted sizes. For more details, see [`FlexSlot`](https://developers.google.com/authorized-buyers/rtb/openrtb-guide#flexslot-object).

Using these fields, identify the best size match for your supported inventory
rather than defaulting to the first available size in the format array.

### Example multi-size request

The following example shows a bid request for a flexible ad slot:

    imp {
      banner {
        w: 800
        h: 50
        format {
          w: 800
          h: 50
        }
        format {
          w: 375
          h: 50
        }
        format {
          w: 300
          h: 50
        }
        format {
          w: 320
          h: 50
        }
        adx_ext {
          flexslot {
            wmin: 300
            wmax: 800
            hmin: 50
            hmax: 50
          }
        }
      }
    }

In this example, the primary size is `800`x`50`. The formats array indicates you
can also bid with creatives of the following sizes:

- `375`x`50`
- `300`x`50`
- `320`x`50`

The `BidRequest.imp.banner.ext.flexslot` field indicates you can bid with any
creative with a width between `300` to `800`, and a height of `50`.