PATIKIL 3 Inch Duct Collar, 2 Pcs Duct Connector Flange Galvanized Iron Tight Vent Air Duct Fitting for Heating Cooling HVAC Ventilation Home Office

Why I reached for this 3-inch duct collar

A lot of airflow issues aren’t solved with bigger fans or louder blowers—they’re solved at the connection points. I picked up this 3‑inch galvanized collar to clean up a few problem vents: a bathroom fan that needed a clean handoff to rigid pipe in the attic, and a compact inline fan that I wanted to mount through a plywood partition in the shop. I was looking for something simple, sturdy, and less leaky than the “tape and hope” approach. This collar delivered that, with a few details worth calling out.

Build and materials

The collar is made from galvanized iron about 0.6 mm thick (roughly 24-gauge), which is a solid, durable thickness for small runs and terminations. It’s noticeably stiffer than the thin stamped sheet you find on disposable boot adapters, and it doesn’t deform when you torque down a hose clamp. The spigot section is corrugated (“wrinkled”) rather than perfectly smooth, which does two things: it gives the duct clamp more bite, and it adds a bit of compliance so you can true up a slightly misaligned connection without creating gaps.

The flange diameter measures about 88 mm (3.5 inches), and the interface outer diameter is around 75 mm (just under 3 inches). That sizing matters: the spigot is designed to slip inside most 3-inch flexible duct or into the female side of 3-inch spiral pipe or a coupler. The flange itself is flat, without a preformed bead or pre-drilled holes on the units I used. The edges are typical of galvanized HVAC fittings—clean cuts but not deburred—so gloves are your friend during handling.

It comes as a two-pack, which turned out to be convenient since one project tends to lead to another.

Installation experience

I used the first collar to create a proper pass-through from a bathroom vent fan into rigid duct in the attic. The sequence was:

• Cut a 3.5-inch circular opening in 1/2-inch plywood sheathing (a hole saw makes this painless).
• Seat the collar flange from the living space side and square it up.
• Fasten the flange with four 3/4-inch self-tapping sheet-metal screws.
• Seal the flange perimeter with butyl or acrylic mastic from the attic side.
• Slide the 3-inch flex over the corrugated spigot, clamp with a 3–3.5 inch worm-drive clamp, then wrap with UL 181 aluminum foil tape.

The second collar went into a 3/4-inch plywood divider on a dust collection branch. Same approach, except I laid a bead of construction adhesive under the flange before driving screws, then sealed further with foil tape on the shop side to discourage fines from escaping.

In both cases, the fit of 3-inch flexible duct over the 75 mm spigot was snug in a good way. I didn’t have to fight it, but once clamped and taped, the connection was rock steady and leak-free on a smoke test. On one rigid-to-rigid trial with 3-inch spiral, I used a short crimped coupler as an intermediary—this collar isn’t a substitute for a standard male crimp, but it will slip into a female end without drama.

Performance and air sealing

This is a passive component, so “performance” is really about minimizing losses. The collar’s flange gives you a flat surface to seal to—much better than trying to mate a round duct directly to a rough opening—and the corrugated spigot encourages a tighter clamp seal than a polished tube would. With mastic at the flange and foil tape around the hose clamp, leakage was effectively zero on my manometer’s low range.

One important point: this collar does not include a backdraft damper or a grille. If you need to prevent reverse airflow, pair it with a separate 3-inch damper or a terminating wall cap that includes one. Used properly, the collar is the stable anchor that makes the rest of that assembly behave.

What it fits (and what it doesn’t)

• Works well with: 3-inch flexible aluminum duct, 3-inch insulated flex, 3-inch spiral pipe (female side), most 3-inch inline fans and adapters with a female port.
• Works with caveats: thin-wall PVC flex hose marketed in 3-inch sizes—measure carefully and clamp; the corrugations help.
• Does not match: Schedule 40 “3-inch” PVC plumbing (OD ~ 3.5 inches). If you’re bridging to plumbing, you’ll need the correct HVAC‑to‑PVC adapter.

The published dimensions were accurate on the collars I received, so if your system is true 3-inch nominal, you should be in good shape.

Practical tips

• Plan your fasteners. The flange is undrilled. Self-tapping screws go in cleanly; predrill if mounting to drywall or thin sheet.
• Seal twice. A bead of mastic at the flange and UL 181 foil tape over the clamped joint beats relying on clamp pressure alone.
• Mind edge safety. A quick pass with a deburring tool or a file on the outer edge will save your knuckles in tight chases.
• Support the run. The collar is sturdy, but it’s not a hanger. Use proper strapping to avoid putting the duct’s weight on the flange.

Durability and corrosion resistance

Galvanized iron is the right choice here. In attic spaces and workshops that see humidity swings, the coating keeps surface rust at bay. After a few weeks in a warm attic, there’s no discoloration and no creep at the fasteners. I wouldn’t hesitate to use it in laundry exhaust or bathroom applications where temperatures and moisture are moderate. For coastal or aggressively corrosive environments, stainless hardware for the screws and clamp is a smart upgrade.

Limitations and things to watch

• No damper, grille, or hood—this is a connector, not a termination kit.
• Not a firestop device—don’t rely on it for rated assemblies.
• Sharp edges—standard fare for HVAC sheet metal but worth noting.
• Code compliance varies—check local requirements for dryer exhaust and penetrations; some jurisdictions are strict about transition materials and sealing methods.

None of these are faults of the collar; they’re just the boundaries of what it’s designed to do.

How it compares

Plastic or ABS collars are common in bathroom fan kits. They’re gentler on hands and can include snap features, but they deform under clamp pressure and don’t love heat. This metal collar is more stable, seals better under a clamp, and feels like a permanent solution rather than a kit part.

You can also make a DIY collar from a short piece of crimped duct, but you’ll fight for a flat sealing surface at the wall or panel, and it’s easy to end up with a wobbly mount. The fixed flange on this unit keeps everything square, which helps reduce stress on the connected duct and prevents long-term migration.

Value

As a two-pack, the price-to-function ratio is strong. Even if you only need one immediately, the spare will find a home—behind a range hood insert, on a small dust collector branch, or as a neat passthrough for a compact inline fan. You get durable material, correct sizing, and a design that encourages airtight installs without messing around.

Final recommendation

I recommend this 3-inch duct collar for anyone who needs a clean, durable way to connect small-diameter duct to a wall, ceiling, floor, or panel opening. The galvanized build is stout, the corrugated spigot grips flexible duct nicely, and the flat flange makes it easy to achieve a leak-free seal with mastic and tape. It’s not a damper or a termination, and it won’t solve code-specific needs on its own, but as a foundational connector in bathroom fans, inline fans, small HVAC branches, and light dust collection, it does exactly what it should and makes the rest of the system better.