Connects rain barrel to downspout that will fill barrel allow water to revert to the downspout when barrel is full. The diverter will fit both a 2x3 inch or a 3x4 inch downspout. The short hose to connect the diverter to the barrel is included.
Some water continues to run through downspout while barrel fills; then all water goes through downspout after barrel is full. Downspout diverters help avoid rain barrels overflowing. Instructions for installation are available here (PDF).
* Downspout diverters are not required for rain barrel function, and are just one method of getting the rain water into the rain barrel. Another alternative is a flex elbow to direct water to the top of the barrel.