Ø90mm Round Sealing Rings (pack of 10 pieces). These sealing rings are an essential part of the AirflexPro range and are used to make an airtight connection on ductwork. These must be fitted on the 3rd trough of the duct, anywhere a duct end connects with another piece. This is to maintain the airtight connection. This pack comes with 10 pieces of sealing rings which are essential for maintaining the secure AirflexPro 90 connection.