•SEMIAFS aluminium semi flexible air ducts are flexible, extendable and highly reliable for low and medium pressure air conditioning, ventilation, boiler systems and chimney liners. •SEMIAFS is elastic, flexible and stretchable. •Oval and circular connectors are easily installed. •SEMIAFS is secured using an “INTERLOCK” crimp system. “INTERLOCK” crimp systems minimize separation of the duct when it is stretched or bent.