A method of making a filter by bonding two pieces of cloth to the flanges of a barrel-neck connector by locating a ring of bonding agent mixed with a metal powder between each flange and the adjacent surface of each cloth and using induction heating to heat the metal and thus cause the bonding agent to bond the cloth to the flanges. The bonding agent may comprise guide legs which allow its accurate location between the respective cloth and flange and/or the ring may be flexible allowing the ring to be flexed into position over the respective flange of the barrel-neck.