Duct Caps | McMaster-Carr

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For Conduit ID

156 Products

Standard Duct and Fittings

Deliver air for a range of HVAC applications, including exhaust and dust collection. Our basic duct, the round shape creates smoother, more efficient airflow than rectangular and oval duct. The male end is slightly smaller than the female, so sections join without clamps or tools.

Vent Caps


Exhaust Vent	Intake Vent

Cover vents with caps that let air in or out.

Exhaust Vent—A built-in damper allows air to escape while blocking backdrafts, rain, and snow.

Intake Vent—Only fresh air enters though the screen—no debris or pests allowed.

Galvanized Steel—Corrosion resistant and affordable, galvanized steel is the most commonly used ductwork material.

Lightweight Aluminum—One-third the weight of steel, aluminum ductwork is easier to handle during installation. Like galvanized steel, it resists rust in wet environments but won’t last as long.

							Galvanized Steel		Lightweight Aluminum
	Duct Size	ID	OD	Ga.	Features	Includes		Each		Each
Exhaust Vent



		3	3"	—	30	—	Backdraft Damper	———	0	0000000	000000


		4	4"	—	30	—	Backdraft Damper	00000000	000000	0000000	00000
		5	5"	—	30	—	Backdraft Damper	00000000	00000	———	0
		6	6"	—	30	—	Backdraft Damper	00000000	00000	———	0
		6	6"	—	22	—	Backdraft Damper	———	0	0000000	00000
		7	7"	—	30	—	Backdraft Damper	00000000	00000	———	0
		8	8"	—	30	—	Backdraft Damper	00000000	00000	———	0
		8	8"	—	22	—	Backdraft Damper	———	0	0000000	000000


		Intake Vent



				4	—	3 7/8"	30	Bird Screen	—	00000000	00000	———	0


				5	—	4 7/8"	30	Bird Screen	—	00000000	00000	———	0
				6	—	5 7/8"	30	Bird Screen	—	00000000	00000	———	0
				7	—	6 7/8"	30	Bird Screen	—	00000000	00000	———	0
				8	—	7 7/8"	30	Bird Screen	—	00000000	00000	———	0

Rain Caps

Top off vertical duct and exhaust stacks to prevent corrosion and blockages that can disrupt airflow.

Galvanized Steel—Corrosion resistant and affordable, galvanized steel is the most commonly used ductwork material.

Corrosion-Resistant 304 Stainless Steel—The most corrosion-resistant metal duct we sell. It won’t rust or degrade in systems that exhaust chemical fumes or vent heat from industrial ovens and dryers.

			Galvanized Steel		Corrosion-Resistant 304 Stainless Steel
Duct Size	ID	Ga.		Each		Each



	3	3"	26	0000000	000000	———	0


	4	4"	26	0000000	00000	0000000	000000
	5	5"	26	0000000	00000	———	0
	6	6"	26	0000000	00000	0000000	00000
	7	7"	26	0000000	00000	———	0
	8	8"	26	0000000	00000	0000000	00000
	9	9"	26	0000000	00000	———	0
	10	10"	26	0000000	00000	0000000	000000
	12	12"	26	0000000	00000	0000000	000000

End Caps

Cover unused duct openings to prevent air from leaking, dust from escaping, and debris from entering. End caps are often used to seal duct after changes to your system or equipment. To make modifications or expand your line, remove the cap.

Galvanized Steel—Corrosion resistant and affordable, galvanized steel is the most commonly used ductwork material.

					Galvanized Steel		Corrosion-Resistant 304 Stainless Steel
	Duct Size	ID	OD	Ga.		Each		Each
Male



		3	—	2 7/8"	26	00000000	00000	———	0


		4	—	3 7/8"	26	00000000	0000	———	0
		5	—	4 7/8"	26	00000000	0000	———	0
		6	—	5 7/8"	26	00000000	0000	———	0
		7	—	6 7/8"	26	00000000	00000	———	0
		8	—	7 7/8"	26	00000000	00000	———	0
		9	—	8 15/16"	26	00000000	00000	———	0
		10	—	9 7/8"	26	00000000	00000	———	0
		12	—	11 7/8"	26	00000000	00000	———	0
		14	—	13 7/8"	26	00000000	00000	———	0
		16	—	15 7/8"	26	00000000	00000	———	0


		18	—	17 7/8"	24	00000000	00000	———	0
		20	—	19 7/8"	24	00000000	00000	———	0
		22	—	21 7/8"	24	00000000	00000	———	0
		24	—	23 7/8"	24	00000000	00000	———	0


		Female



				3	3"	—	26	00000000	0000	0000000	000000


				4	4"	—	26	00000000	0000	0000000	00000
				5	5"	—	26	00000000	0000	———	0
				6	6"	—	26	00000000	0000	0000000	00000
				7	7"	—	26	00000000	00000	———	0
				8	8"	—	26	00000000	00000	0000000	00000
				9	9"	—	26	00000000	00000	———	0
				10	10"	—	26	00000000	00000	0000000	000000
				12	12"	—	26	00000000	00000	———	0
				14	14"	—	26	00000000	00000	———	0
				16	16"	—	26	00000000	00000	———	0


				18	18"	—	26	00000000	00000	———	0
				20	20"	—	24	00000000	00000	———	0
				22	22"	—	24	00000000	00000	———	0
				24	24"	—	24	00000000	00000	———	0

Quick-Disconnect Duct and Fittings

The fastest ductwork to disassemble for dust collection and other frequently cleaned systems. Join sections with quick-release clamps that open and close with a flip of the latch. Since you don’t need screws, welds, or tools, the installation time is half that of other duct types.

End Caps

Galvanized Steel—Corrosion resistant and affordable, galvanized steel is the most commonly used ductwork material.

			Galvanized Steel		Corrosion-Resistant 304 Stainless Steel
Duct Size	ID	Ga.		Each		Each



	3	2 7/8"	18	00000000	000000	———	0


	3	3 1/16"	22	———	0	00000000	000000
	4	3 7/8"	22	00000000	00000	00000000	00000
	5	4 7/8"	22	00000000	00000	00000000	00000
	6	5 7/8"	22	00000000	00000	00000000	00000
	7	6 7/8"	22	00000000	00000	00000000	00000
	8	7 7/8"	22	00000000	00000	00000000	00000
	9	8 7/8"	22	00000000	00000	00000000	00000
	10	9 7/8"	22	00000000	00000	00000000	00000
	12	12"	22	00000000	00000	00000000	00000
	14	13 15/16"	20	00000000	00000	00000000	00000


	16	16"	20	00000000	00000	00000000	00000
	18	17 7/8"	20	00000000	00000	———	0
	18	17 15/16"	20	———	0	00000000	00000
	20	19 7/8"	20	00000000	00000	———	0
	20	19 15/16"	20	———	0	00000000	00000
	22	21 7/8"	20	00000000	00000	———	0
	24	23 7/8"	20	00000000	00000	———	0

Spiral Duct and Fittings

Reinforced with a continuous seam, this duct keeps its shape, even against suction from dust collection systems. On the inside, duct is smooth for efficient airflow. Because of its attractive look, spiral duct is often used for exposed heating and cooling systems.

End Caps

Galvanized Steel—Corrosion resistant and affordable, galvanized steel is the most commonly used ductwork material.

		Galvanized Steel			Corrosion-Resistant 304 Stainless Steel
Duct Size	OD	Ga.		Each	Ga.		Each
3	2 7/8"	24	0000000	000000	24	00000000	000000
4	3 7/8"	24	0000000	00000	24	0000000	00000
5	4 7/8"	24	0000000	00000	24	00000000	00000
6	5 7/8"	24	0000000	00000	24	0000000	00000
7	6 7/8"	24	00000000	00000	24	00000000	00000
8	7 7/8"	24	0000000	00000	24	0000000	00000
9	8 7/8"	24	00000000	00000	24	00000000	00000
10	9 7/8"	24	0000000	00000	24	0000000	00000
12	11 7/8"	24	0000000	00000	24	00000000	00000
14	13 7/8"	24	0000000	00000	24	00000000	000000
16	15 7/8"	24	0000000	00000	24	00000000	000000
18	17 7/8"	22	00000000	00000	24	00000000	000000
20	19 7/8"	24	00000000	00000	24	00000000	000000
22	21 7/8"	24	00000000	00000	—	———	0
24	23 7/8"	24	00000000	00000	—	———	0

Tight-Seal Spiral Duct and Fittings

Gasketed fittings prevent leaks between connections without the need for tape or other sealants. Duct has a continuous seam that reinforces it for strength and long life. The rigid construction keeps its shape, even against suction from dust collectors. Duct is smooth on the inside for efficient airflow. Because of its attractive look, spiral duct is often used for exposed heating and cooling systems.

End Caps

Galvanized Steel—Corrosion resistant and affordable, galvanized steel is the most commonly used ductwork material.

		Galvanized Steel with EPDM Gasket
Duct Size	OD	Ga.		Each
4	3 7/8"	24	0000000	000000
6	5 7/8"	24	0000000	00000
8	7 7/8"	24	0000000	00000
10	9 7/8"	24	0000000	00000
12	11 7/8"	24	0000000	00000

Chemical-Resistant Duct and Fittings

Chemicals can eat away at most metal duct, but not this PVC system. It’s often used to exhaust corrosive gases, vapors, and fumes. Components press-fit together and secure with PVC pipe cement.

Rain Caps

Prevent blockages that can disrupt airflow in vertical duct and exhaust stacks. These caps keep water and debris from entering your system.

			PVC
Duct Size	ID	Color		Each



	4	4 1/2"	Gray	000000	0000000


	6	6 5/8"	Gray	0000000	000000
	8	8 5/8"	Gray	0000000	000000
	10	10 3/4"	Gray	0000000	000000
	12	12 3/4"	Gray	0000000	000000
	14	14"	Gray	0000000	000000

End Caps

			PVC
Duct Size	ID	Color		Each



	4	4 1/2"	Gray	00000000	000000


	6	6 5/8"	Gray	00000000	000000
	8	8 5/8"	Gray	00000000	000000
	10	10 3/4"	Gray	00000000	000000
	12	12 3/4"	Gray	00000000	000000
	14	14"	Gray	00000000	000000

Duct Vent Caps


Wall Mount	Sloped Roof Mount

Cover wall and roof vents to prevent cold air and debris from entering your system. These caps have damper to reduce backdrafts and a screen that blocks birds from sneaking in.

Painted Steel—Strong for a long life, these caps have a black finish to prevent rust.

	For Duct						Mounting			Painted Steel
	Ht.	Wd.	Dia.	Ht.	Wd.	Lg.	Fasteners Included	Hole Dia.	Color		Each
Wall Mount







				For Rectangular Duct

				10"	3 1/4"	—	5 5/8"	12 3/4"	8 7/8"	No	3/16"	Black	0000000	000000


				Sloped Roof Mount







								For Rectangular and Round Duct

								10"	3 1/4"	8"	6 5/8"	14 1/4"	18 3/4"	—	—	Black	0000000	00000

Rectangular Duct and Fittings

Maximize the space in close quarters, such as inside walls and ceilings. As rectangular duct sizes increase, they get wider but not taller. This shape is most often used for heating and cooling inside buildings. Components connect with brackets.

End Caps

Cover unused duct openings to prevent air leaks. End caps are often used to seal duct after changes to your system or equipment. To make modifications or expand your line, remove the cap.

Galvanized Steel—Corrosion resistant and affordable, galvanized steel is the most commonly used ductwork material.

			Galvanized Steel
Wd.	Ht.	Ga.		Each



	8"	8"	28	0000000	00000


	10"	8"	28	0000000	0000
	12"	8"	28	0000000	00000
	14"	8"	28	0000000	00000
	16"	8"	26	0000000	00000
	20"	8"	26	0000000	00000
	24"	8"	26	0000000	00000

Expansion Plugs for Conduit

Seal conduit openings to keep water, dirt, and animals from damaging your wiring. When you twist the nut on top of these plugs, a rubber seal expands to close off the end of your conduit. Tie a rope or pull line to the loop at either end of these plugs to hold them in place during installation.

	For Conduit			Material
	Trade Size	ID	Overall Ht.	Seal	Loop	Features		Each
Loop Nut—Plastic Plate



		3/4	0.77" to 1.02"	3 1/4"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	00000


		1	0.99" to 1.39"	3 3/4"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	0000
		1 1/4	1.16" to 1.51"	3 13/16"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	0000
		1 1/2	1.46" to 1.83"	4"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	0000
		2	1.83" to 2.39"	4"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	0000
		2 1/2	2.4" to 2.99"	7 1/2"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	00000
		3	2.92" to 3.45"	7 5/8"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	00000
		3 1/2	3.41" to 3.9"	8 3/16"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	00000
		4	3.94" to 4.33"	7 1/2"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	00000
		5	4.85" to 5.25"	7 5/8"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	00000
		6	5.92" to 6.37"	10 5/8"	Synthetic Rubber	Plastic	Internal Eyebolt	0000000	00000