Model # R4X3

Internet # 100149942

Store SKU # 148814

Store SO SKU # 1000684915

4 in. To 3 in. Round Reducer

$5.85 /each

Frequently Bought Together

Product Overview

Master Flow Round Reducers are used to decrease the diameter of the pipe when making connections in an HVAC system. Hemmed collar edges make these Reducers especially strong and snug-fitting. They can also be used to increase pipe diameter if necessary.

  • Hemmed collar edges improve fit and increase strength
  • Also used to increase pipe size
  • Galvanized steel construction
  • Always seal seams with building code approved sealant or duct tape
  • Always insulate ductwork for greater system efficiency and comfort

Info & Guides

You will need Adobe® Acrobat® Reader to view PDF documents.  Download a free copy from the Adobe Web site.



Product Depth (in.) 
Product Height (in.) 
Product Width (in.) 
4 in 


Brand/Model Compatibility 
HVAC application 
All HVAC types 
Product Weight (lb.) 
0.33 lb 

Warranty / Certifications

Manufacturer Warranty 
Free from Manufacturer Defect at Time of Delivery. 

More Products With These Features


Customer Questions & Answers

1 Question0 Answers

Customer Questions & Answers

4 in. To 3 in. Round Reducer
4 in. To 3 in. Round Reducer

Ask your questions. Share your answers.

Clear Search Term
This question is from 4 in. To 3 in. Round Reducer
0 answers

Can this be used on a 4" metal corrugated tubing coming from a dryer going into the 3" wall connection?

This question is from 4 in. To 3 in. Round Reducer
Asked by
Read all my Q&A
January 3, 2016
0out of 0found this question helpful.
Was this helpful?helpful0unhelpful0
1 of 1
  • 2016-07-25 T20:30:10.526-05:00
  • bvseo_lps, prod_bvqa, vn_prr_5.6
  • cp-1, bvpage1
  • co_hasquestions
  • loc_en_US, sid_100149942, prod, sort_default
1 of 1
  • bvseo_sdk, java_sdk, bvseo-3.1.1
  • CLOUD, getContent, 243ms

Customer Reviews

Rated 4.5 out of 5 by 15 reviewers.
Rated 5.0 out of 5.0 by Just What Was Needed I bought this because my new bath fan required a 4 inch duct but my old bath fan used a 3 inch duct. Normally you want to replace the entire duct, however the area where my 3 inch duct reached the exit vent was sealing in spray foam insulation that hardens. Rather than deal with all that I opted to use this reducer. This saved a lot of time and everything worked out great. April 30, 2015
Rated 5.0 out of 5.0 by Great product My uncle owned a sheet metal shop and I worked with him for many years while working for an industral plant. I made some reducers both in square and round and these products are as good as I have seen. December 29, 2015
Rated 4.0 out of 5.0 by Saved the day! Great option if you don't know what size duct you have in an existing unit. I purchased a bathroom vent fan with a 4" duct to replace an existing. I was able to remove the existing unit without damaging the drywall (Saves a ton of time). However, the existing duct was 3". So this product saved me a ton of time. December 8, 2015
Rated 5.0 out of 5.0 by Master flow, Great product, I pass my city inspection.easy to install. October 13, 2015
Rated 5.0 out of 5.0 by Well made product. I use these for work some times and I was glad to find when I went to grab one of these 4"-3" reducers it was of the better quality made than some of the lesser quality I have seen in the past. June 16, 2015
Rated 4.0 out of 5.0 by Served it's purpose Works like it should, and truly the best option for reduction on my vent fan. April 21, 2015
Rated 1.0 out of 5.0 by Product was damaged during manufacturing and took me an extra half hour to get it to fit properly. Product was not looked at prior to shipping and was sent damaged causing me extra time to repair it. March 10, 2015
Rated 4.0 out of 5.0 by Good quality Good adapter watch out for sharp edges, don't forget the foil tape to seal the connections. December 30, 2014
  • 2016-07-24 T19:27:57.192-05:00
  • bvseo_lps, prod_bvrr, vn_prr_5.6
  • cp-1, bvpage1
  • co_hasreviews, tv_15, tr_15
  • loc_en_US, sid_100149942, prod, sort_default
2 >>
  • bvseo_sdk, java_sdk, bvseo-3.1.1
  • CLOUD, getContent, 244ms