It permits you to quickly and securely attach the hose to a circular access opening in an air duct. The adapter attaches easily to the vacuum hose using a hose clamp or tape. The assembly can then be snapped into place (no screws, tape or clamps) in the air duct opening using the mechanical attachment ears built into the adapter. This device not only makes attachment a breeze, it also significantly increases airflow during the job because its low profile in the air duct offers so little obstruction to airflow from the duct into the hose. This allows your vacuum system to work more efficiently all through the cleaning. Working ports in the body of the adapter allow you to insert agitation tools while the vacuum hose is connected. Available in 8 inch, 10 inch and 12 inch sizes.