Flexible connectors are used in ducting systems to reduce vibration transmission, shock and accommodate thermal movements with minimum stress to the ductwork. Since pressure requirements in ducts are very low compared to piping systems, they are manufactured in lighter construction to be more responsive to the reduced stiffness of sheet metal ducting. Designs are always airtight to prevent particle intake or leakage. These products come in many configurations as no standard design can meet the varied scope, service or connection requirements. They can be round, square, rectangular, round on one end and square on the other and even “T" or “L" shaped. Concentric and Eccentric Reducers are common and custom made designs can be made to offset or compensate for older misaligned heavy ducting systems. The common characteristics are flexibility and long life. Motion requirements are met with single and multiple arches and by varying the face to face length.