# Ducting diameter for mailbox mod



## howea (Jun 19, 2022)

I'm planning to do the mailbox type mod and noticed everyone seems to use the semi-rigid ducting is 3", which is not available in New Zealand.
I can get 4"+ and 2" (the 2" is actually stainless exhaust hosing)

Which one would be better to get?


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## Steve H (Jun 20, 2022)

I'm using 2"stainless pipe on mine. Works fine.


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## chopsaw (Jun 20, 2022)

I have 4" coming out of the mailbox , then it necks down to 3" when it rises . 2 or 4 works as long as you can get the flow . 
I use the 4" for a chamber of low pressure to get the smoke moving out of the mailbox .


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## cmayna (Jun 20, 2022)

I believe mine starts at 4" at the mailbox and reduces down to 3" as it connects to the chip feed hole of the MES


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## tallbm (Jun 20, 2022)

howea said:


> I'm planning to do the mailbox type mod and noticed everyone seems to use the semi-rigid ducting is 3", which is not available in New Zealand.
> I can get 4"+ and 2" (the 2" is actually stainless exhaust hosing)
> 
> Which one would be better to get?


Hi there and welcome!

The 3 inch is used because that is the size of the chip feeder contraption's hole.  So you could take your 4 inch and then make a perpendicular cut to the end that goes into the MES and just kinda force it to overlap and then "bolt" or fasten it so that it stays 3 inch.  Cover any caps with aluminum flue tape and boom problem solved.

This is all in theory as I have not done it.  You may need to take a straight 4 inch duct and cut it long ways so you can do the same kind of thing but place it over the 4inch elbow on one side and use wurm tape to "fasten" it in place and then do the same thing with the MES side for a 3inch hole then cover in flue tape. 

You get the idea... provided I explained it well :D


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## howea (Jun 20, 2022)

Sounds like 4" is the way to go (allows more flow)

My smoker cabinet is custom built, so I got no feeder inlets etc


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## chopsaw (Jun 21, 2022)

howea said:


> Sounds like 4" is the way to go (allows more flow)
> 
> My smoker cabinet is custom built, so I got no feeder inlets etc


The only reason I necked mine down was to fit the 3 inch inlet on an MES 30 . 
I have a fitting at the mailbox that has a shoulder on it . 
Cut the hole , slide the fitting in against the stop and bend the fingers over on the inside of the mailbox . Nice clean connection . No need for tape . 
Hard to see in the picture .


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