--- product_id: 260366285 title: "Duct Increaser and Reducer, Plastic Inline Adapter, White, 4” to 3” (IRB43)" brand: "deflecto" price: "€ 26.62" currency: EUR in_stock: true reviews_count: 5 category: "Deflecto" url: https://www.desertcart.be/products/260366285-duct-increaser-and-reducer-plastic-inline-adapter-white-4-to store_origin: BE region: Belgium --- # 4" to 3" seamless duct transition 325°C heat-resistant polypropylene Lightweight at just 22.7g Duct Increaser and Reducer, Plastic Inline Adapter, White, 4” to 3” (IRB43) **Brand:** deflecto **Price:** € 26.62 **Availability:** ✅ In Stock ## Summary > 🔄 Upgrade your airflow game with seamless duct transitions! ## Quick Answers - **What is this?** Duct Increaser and Reducer, Plastic Inline Adapter, White, 4” to 3” (IRB43) by deflecto - **How much does it cost?** € 26.62 with free shipping - **Is it available?** Yes, in stock and ready to ship - **Where can I buy it?** [www.desertcart.be](https://www.desertcart.be/products/260366285-duct-increaser-and-reducer-plastic-inline-adapter-white-4-to) ## Best For - deflecto enthusiasts ## Why This Product - Trusted deflecto brand quality - Free international shipping included - Worldwide delivery with tracking - 15-day hassle-free returns ## Key Features - • **Sleek White Finish:** Clean, professional look that blends seamlessly with modern home ventilation systems - • **Space-Smart Compactness:** Slim profile and lightweight build make it perfect for tight bathroom fan setups - • **Universal Compatibility:** Bridges 4" dryer exhausts to 3" ducts flawlessly, ensuring optimal airflow - • **Heat-Resistant Durability:** Crafted from polypropylene with a 325°C melting point to withstand high temps safely - • **Effortless Fit & Flexibility:** Slip-on design for quick, clamp-secured installation—no fuss, no tools needed ## Overview The Deflecto Duct Increaser and Reducer (IRB43) is a lightweight, durable plastic adapter designed to connect 4-inch ducts to 3-inch ducts effortlessly. Made from heat-resistant polypropylene with a melting point of 325°C, it ensures safe and reliable performance in bathroom fan and dryer exhaust installations. Its slip-on design allows for quick setup, making it an essential upgrade for efficient home ventilation. ## Description Adapt your 3” duct to a 4” exhaust hood with the Deflecto Duct Increaser and Reducer. This polypropylene plastic connector is an ideal connector when installing bathroom fans as well. Slip the ducts over the ends of the increaser/reducer, and tighten down with clamps (not included). Durable and lightweight, this reducer has a melting point of approximately 325 degrees F. Deflecto was founded on innovative, problem solving products. For over a half century, we have built a tradition of discovering and meeting needs with invention and dependable manufacturing. Today, Deflecto is the world’s largest chair mat, bicycle reflector and dryer venting manufacturer and a global leader in sign and literature holders, office workspace accessories and other air distribution products. Review: Worked perfectly for the larger air pump I added to my wecreat 45w pro laser Review: I used mine to go from 3” to 4” (expander) rather than reducer and it did the job I wanted. ## Features - Designed to transition between 4" and 3" diameter ducts - Simply slip the ducts over the increaser/reducer, tightening in place with clamps (not included) - Durable polypropylene construction has a melting point of approximately 325 degrees - Connects a 4 inch dryer exhaust hood to a 3 inch duct - Ideal for bathroom fan installations ## Technical Specifications | Specification | Value | |---------------|-------| | ASIN | B005XU3QCQ | | ASIN | B005XU3QCQ | | Batteries Included? | No | | Batteries Required? | No | | Best Sellers Rank | #45,955 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #50 in Heating & Cooling Ducting Products | | Color | White | | Customer Reviews | 4.3 4.3 out of 5 stars (733) | | Customer reviews | 4.3 4.3 out of 5 stars (733) | | Date First Available | 17 June 2010 | | Date First Available | 17 June 2010 | | Department | Electronics | | Included components | Deflecto Duct Plastic Increaser and Reducer, 4" to a 3", (IRB43) | | Is Discontinued By Manufacturer | No | | Item Package Quantity | 1 | | Item Weight | 22.7 g | | Item model number | IRB43 | | Item model number | IRB43 | | Manufacturer | Deflecto | | Manufacturer | Deflecto | | Material | Plastic | | Number Of Pieces | 1 | | Part number | DEFIRB43 | | Product Dimensions | 10.16 x 8.64 x 10.16 cm; 22.68 g | | Product Dimensions | 10.16 x 8.64 x 10.16 cm; 22.68 g | | Special Features | Lightweight | ## Images ![Duct Increaser and Reducer, Plastic Inline Adapter, White, 4” to 3” (IRB43) - Image 1](https://m.media-amazon.com/images/I/71ynkr5cqxL.jpg) ## Customer Reviews ### ⭐⭐⭐⭐⭐ Review *by D***. on 26 March 2026* Worked perfectly for the larger air pump I added to my wecreat 45w pro laser ### ⭐⭐⭐⭐⭐ Review *by P***R on 1 January 2025* I used mine to go from 3” to 4” (expander) rather than reducer and it did the job I wanted. ### ⭐⭐⭐⭐⭐ Review *by A***I on 22 May 2018* As others have said the 4 inch side is the same size as the 4" outlet duct on newer bathroom vent fans BUT I used a hot glue gun to essentially "weld" the two plastic pieces together. To assure a strong connection I wrapped the joint afterward with silicone self adhesive tape. I imagine duct tape would also work. The existing 3" flexible duct was a snug fit, but with a little effort it went over the 3" side of the reducer. I considered using a galvanized steel 3x4 duct adapter (Home Depot, Menards) but because of all the shower moisture being vented out I was concerned with the piece rusting over time. The plastic reducer was cheaper and will be rust-free. ## Frequently Bought Together - Deflecto Duct Increaser and Reducer, Plastic Inline Adapter, White, 4” to 3” (IRB43) - Daisypower Dryer Vent Window Kit, Adjustable Window Vent Kit with Outdoor Dryer Vent Cover,4 Inch Hood for Exhaust Ventilation - AC Infinity Flexible 4-Inch Aluminum Ducting, Heavy-Duty Four-Layer Protection, 8-Feet Long for Heating Cooling Ventilation and Exhaust --- ## Why Shop on Desertcart? - 🛒 **Trusted by 1.3+ Million Shoppers** — Serving international shoppers since 2016 - 🌍 **Shop Globally** — Access 737+ million products across 21 categories - 💰 **No Hidden Fees** — All customs, duties, and taxes included in the price - 🔄 **15-Day Free Returns** — Hassle-free returns (30 days for PRO members) - 🔒 **Secure Payments** — Trusted payment options with buyer protection - ⭐ **TrustPilot Rated 4.5/5** — Based on 8,000+ happy customer reviews **Shop now:** [https://www.desertcart.be/products/260366285-duct-increaser-and-reducer-plastic-inline-adapter-white-4-to](https://www.desertcart.be/products/260366285-duct-increaser-and-reducer-plastic-inline-adapter-white-4-to) --- *Product available on Desertcart Belgium* *Store origin: BE* *Last updated: 2026-04-30*