By default, the barrel of the dreamline is free floating. This means that the barrel does not come into contact with the air tube or stock.
In many cases this is positive for the precision of the rifle.

However, this can cause the rifle to be sensitive to POI shifts as a result of movement of the barrel after it has (for example) been roughly transported in a rifle bag.

This barrel band can prevent this by creating a solid connection between the barrel and the air tube.