Lambro Industries 121IND Aluminum Transition Fitting

Product Description

The LAMBRO INDUSTRIES 121IND is a round-to-rectangular aluminum transition fitting used to connect 5-inch round duct to 3-1/4 inch by 10-inch rectangular duct sections. This type of fitting is a standard component in residential and light commercial HVAC duct systems, allowing installers to transition between round flex or rigid duct and flat rectangular duct runs. Fabricated from aluminum, the fitting resists moisture and corrosion in typical conditioned-air applications. HVAC technicians and sheet metal installers use this fitting during new construction and duct modification work where a round-to-rectangular offset is required.

This transition fitting is suited for residential forced-air heating and cooling systems where 5-inch round supply or return branches connect to 3-1/4 inch by 10-inch rectangular duct. Common installation scenarios include under-floor crawlspace duct runs, wall cavity transitions, and equipment room takeoffs. The fitting is sold individually and ships in its own box, making it straightforward to order for single-unit replacements or multi-unit rough-in work.

Key Features

• Transitions 5-inch round duct to 3-1/4 inch by 10-inch rectangular duct in a single fitting
• Aluminum construction resists corrosion in conditioned-air duct environments
• Individual packaging keeps the fitting protected and ready for installation
• Compact, single-unit sell quantity simplifies ordering for service and replacement work

Compatibility

Designed as an OEM-style replacement or new-installation fitting for residential and light commercial forced-air duct systems requiring a 5-inch round to 3-1/4 inch by 10-inch rectangular transition.

Installation Notes

This fitting is installed by licensed HVAC technicians or sheet metal mechanics as part of a ducted air distribution system. Shut down the air-handling unit and confirm the system is de-energized before modifying any duct section. Seal all joints with UL 181-listed mastic or foil tape per local mechanical code requirements. Secure the fitting to adjoining duct sections with sheet metal screws at standard intervals before applying sealant.

Technical Specifications

• Round Duct Connection: 5 inches
• Rectangular Duct Connection: 3-1/4 inches x 10 inches
• Material: Aluminum
• Weight: 0.85 pounds
• Package Quantity: 1 each

Standard Information

• Brand: LAMBRO INDUSTRIES
• Manufacturer Part Number: 121IND