What do I do when wrong flex diameter for branch?
Flex Duct Connections & SupportsPolished core starter — flex/manufacturer check
Wrong flex diameter is not a field “make it fit” problem. Verify size against print/boot/collar before installing.
Field checklist
- Read size on flex, collar, boot, or tag.
- Compare to drawing/shop sheet.
- Do not stretch/crush to fit.
- Separate wrong size material.
- Ask foreman before using reducers or substitutes.
Ask foreman
This flex diameter does not match the branch/boot. Do you want me to get the correct size or use an approved reducer?
Do not
Do not force the wrong flex size onto a collar.
Why it matters
Wrong size changes airflow and creates bad connections.
Search words: flex collar support size mismatch