They are ideal for extending ducting runs.
Female or Male Ducting Threaded Joiner Connector Flexible Tumble Dryer 4" 5" 6"
150mm Galv Male Metal Spiral & Flexible Ducting Connector Coupler Extractor Fans
125mm Galv Male Spiral Metal & Flexible Ducting Connector/Coupler Extractor Fans
CZQC PC Water Cooling Adapter Black G1/4 6mm Male to Male Extender Connector Joiner Fitting with Sealed O-Ring for Computer Water Cooling Systems
Maxmoral 5PCS PWM Plastic Shell Computer Case Cooling Fan Male Plug Interface 4-pin PC Fan Connector Kit
Ventilation T Piece 4 5 6 8 10 12 Inch Ducting Connector Grow Room Hydroponics
