The 4-Inch Dust Control Flex Cuff with Key Hose Clamps by POWERTEC.

This coupler is designed to provide you with an airtight connection between a pair of 4" dust collection fittings or hoses. And it comes equipped with standard hose clamps so that you won't need unattractive duct tape or a messy assortment of screws.
It's a highly useful (and reusable) dust collection system accessory, as it allows you to interchange fittings and connect adapters to keep all of your dust collection tools connected.

Connected 4" PVC pipe to 4" blast gate
Joined a table saw to a dust sheriff as a temporary solution
Connected a 4" table saw sawdust exit to a shop vac adapter
Used along with the POWERTEC 4” Reducer to connect a shop vac to planer
“No matter whether you own one or five of these, the wide range of practical applications are endless.”

Dimensions of Rubber Connector Cuff
4-9/16-Inch OD
4-Inch ID

The 4-Inch Dust Collector System 90 Degree Elbow by POWERTEC.
This convenient adapter serves as a versatile, yet highly functional attachment and tool for common 4 inch dust collector fittings. Whether you're adding a sweep to a small shop vacuum dust collection system or running a hose to an overhead mainline, this elbow attachment is made to deliver an airtight connection to your dust collection hoses and vacuum pipes.
With its high friction grip, this durable connector will ensure that harmful abrasives, dust and debris are all extracted straight into your dust collector. This helps ensure that clear, clean air are put back into your workshop environment.

Product Dimensions (important specification information)
Both 4-inch nominal ends measure precisely at:
3-61/64-inch tapered outer diameter
3-3/4-inch inner diameter