Cleaning Clay Flue - What size brush?

[Wood Pirate]

My clay flue to my wood boiler measures 6-1/4" X 6-1/2".

Is a 7"x7" brush best?

In the past I never had the perfect brush so only used what I had. I would like to order the perfect size?

Thanks

 

[strawman]

I have the same size flue and brush however, when I built my chimney I left the liner up about 3-4feet so the brush could "spring free" when I got thru the bottom. I've never tried to pull the brush up before it cleared. Don't know if I could. I would only go a foot or so the first time just to make sure you can pull it back. Getting it down and not back up would be a dilema to say the least

 

[Todd]

Get a 7" brush and trim it down to perfect fit.