Air Flow Products 77202018 Transition Boot 20x20 18 Inch

Product Description

The AIR FLOW PRODUCTS 77202018 is a straight transition boot with flange, designed to connect a square or rectangular duct opening to a round collar in low-pressure supply or return air duct systems. Built to the 77F configuration, it transitions from a 20x20 inch square opening to an 18 inch round collar, allowing installers to adapt plenum or trunk-line duct runs to round branch takeoffs. HVAC technicians and sheet metal contractors install this fitting during new construction or system modification work where a clean, flanged connection is required at the air handler, grille, or diffuser interface.

This boot is suited for residential and light commercial forced-air HVAC installations. The flanged design simplifies attachment to ceiling, floor, or wall openings, providing a secure mounting surface for grille or diffuser fastening. The straight geometry keeps airflow transitions direct with minimal turbulence, making it appropriate for supply trunk extensions and return air plenums that require a square-to-round adapter at the termination point.

Key Features

• Straight transition geometry from 20x20 inch square to 18 inch round collar
• Flanged perimeter provides a positive mounting surface for grille or diffuser attachment
• 77F configuration designed for direct, low-offset duct transitions
• Sized for high-volume branch or trunk terminations in forced-air systems

Compatibility

Designed as an OEM-style sheet metal fitting for use in residential and light commercial forced-air duct systems requiring a square-to-round transition at a 20x20 inch duct opening with an 18 inch round collar.

Installation Notes

Installation is typically performed by licensed HVAC technicians or sheet metal contractors. Shut down the air handling unit and lock out power before connecting or sealing any duct fitting. Secure the boot to the duct opening with sheet metal screws and seal all joints with UL 181-rated mastic or foil tape per local mechanical code requirements. Verify that the round collar connection to the branch duct is properly supported to prevent stress on the joint.

Technical Specifications

• Configuration: 77F Straight Transition with Flange
• Transition Type: Square to Round
• Square Opening Size: 20x20 inches
• Round Collar Diameter: 18 inches

Standard Information

• Brand: AIR FLOW PRODUCTS
• Manufacturer Part Number: 77202018