will this work on connecting a 6" cast iron to a 4" clay sewer line??

No, the 4" side on the P1056-64 is a nominal 4.46" inside diameter according to Fernco so it too small for 4" clay. The Fernco 1002-46 is designed for 6" PVC/cast iron to 4" clay and according to Fernco.com has a 6.39" by 5.18" inside diameter. Haven't worked with clay pipe but according to the sizing information from the Fernco site, any adapter with a clay connection requires that side of the adapter to be sized just for clay. Hope this helps.

Will this work on connecting a 6" dsw sch 40 pvc pipe to a sdr 35 4" pipe?

It will work but because sdr 35 is thinner wall than sch 40 be careful not to over tighten the connection to the 35.

What are the inner diameter dimensions?

Its difficult to measure as it is flexible and not perfectly round when not installed on a pipe. As close as I can get the inside diameters are 4 1/2 and 6 1/2 inches. Fits 4 inch schedule 40 PVC and the top fitting on a IBC container which is what I used it for.

12"coupling reduce to 6"

No. Mine fit loosely on an 8" to 6".

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Fernco, 1056-64, Flexible Coupling, For Pipe Size 6" x 4"

Product ID: 9285975

Details

Brand
Fernco
Color
Black
Connector Type
Coupling
Exterior Finish
Black
Item Weight
0.81 Pounds
Item dimensions L x W x H
4.8 x 6.81 x

🌍Underground rated for durability

🔧Fast, tool-friendly installation

⚙️6" x 4" flexible coupling size

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€ 40.83

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Sold byAmazon CroatiaDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

🔗 Connect with confidence—flexibility meets durability in every seal!

TOOL READY INSTALLATION - Install quickly with just a screwdriver, nut driver, or socket wrench—no fuss, no delay.
RELIABLE LEAK PROOF SEAL - Engineered to provide a positive, watertight seal for vent, drain, sewer, and waste piping.
TRUSTED INDUSTRY STANDARD - From a USA manufacturer with a 4.6-star rating, backed by decades of plumbing innovation.
BUILT FOR HARSH ENVIRONMENTS - Underground rated to withstand tough conditions and ensure long-lasting performance.
SEAMLESS MULTI MATERIAL COMPATIBILITY - Connects cast iron, PVC, steel, copper, and lead pipes effortlessly.

The Fernco 1056-64 Flexible Coupling is a 6" x 4" high-performance pipe connector designed for quick installation and reliable sealing across multiple pipe materials including cast iron, PVC, steel, copper, and lead. Underground rated and engineered for vent, drain, sewer, and waste systems, it offers a durable, leak-proof solution trusted by professionals and homeowners alike.

Specifications

ASIN	B000BQM0JC
Best Sellers Rank	#116,277 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #3,697 in Pipe Fittings
Brand Name	Fernco
Color	Black
Connector Type	Coupling
Customer Reviews	4.6 4.6 out of 5 stars (155)
Exterior Finish	Black
Global Trade Identification Number	00018578000131, 00018578015586
Included Components	P1056-64 Flexible PVC Pipe Coupling
Item Dimensions	4.8 x 6.81 x 5.56 inches
Item Type Name	Flexible PVC Pipe Coupling
Item Weight	0.81 Pounds
Manufacturer	Fernco Inc.
Manufacturer Part Number	P1056-64
Manufacturer Warranty Description	Warranty
Material Type	Polyvinyl Chloride
Model Number	1056-64
Number of Pieces	1
Size	6" x 4"
Thread Size	6.85 inches
Thread Type	NPT
UPC	018578015586 018578000131
Unit Count	1.0 Count

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