4Pcs 5mm Rigid Flange Shaft Coupling, Guide Shaft Support Coupler High Hardness Metal Axis Bearing Fittings Motor Connector

I've bought multiple sizes and all have been the same quality so I'm posting the same review for all.Inside diameter fits the motor shaft very well and the face is perpendicular to the shaft. The small set screws and threaded holes they go into fit perfect. Even the hex wrench that's included is strong. The parts have no burrs or sharp edges.

The quality is very good and the package has the right amount of fastners.

These 5mm shaft couplers are pretty good quality & could have been a 5 if it was not for the screw hole burrs. The screw holes are for the coupler 'set screws' to lock it onto the motor shaft. It took me hours to de-burr the 4 couplers AND I had to buy a metal wire brush set (see below) to do so. Once de-burred, these couplers go on easily. You can probably hammer the coupler onto the motor shaft, but you will not be able to remove it - you'll probably need a gear/wheel puller (and hope you don't damage the coupler in the process).The wire brush set which saved the day was...https://www.amazon.com/Carburetor-Cleaner-Cleaning-Brushes-Small/dp/B075J7M7B4/ref=sr_1_2?dchild=1&keywords=Carb+Carburetor+Cleaner+Cleaning+Brushes+Kit&qid=1586282681&sr=8-2

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They are 4mm. Worked great for what I wanted them.

Nice product & reasonable price.

Appreciated that it came with wrenches

They wouldn't fit over the 5mm shaft on my NEMA 17 motors. Fortunately for me, I had a 5mm reamer to clean out the burs or the excess plating that prevents them from slipping over the shaft. It would have been an okay press fit, if that's what you're going for.