I bought a few of these for the first time. I thought it would save time, space and effort in locking together a few of the 2' wheels. At best they were ok. It could have been better if I would have done more work and realized which bolts I had on-hand and not.. We had to get creative with our screws and washers to get these to work.
So far so good.

The threads are no issues even after many installations. The screw on the opposite side of the D cut transfers lots of torque.
I wish it was steel though because the bore started to wear out

These nubs require threading and are easily broken. When changing the wheels on our tile runner, we had to purchase new nubs because at least half of them broke.

From the AndyMark Support Team:
We're sorry to hear that the Nubs were breaking. This sounds like an odd situation.
With any questions about out products or how to use them, feel free to call ([****], 9-5 Eastern Time) or email us ([****]) and we're happy to help.

We purchased the am-3669 nubs intending to use them to mount 5mm hex shafts to arms and other 'fixed' components such as dead-axles on wheels. Unfortunately, there's little to no consistency in the hex pattern alignment relative to the rest of the nub, meaning they can't be reliably used in pairs.

We've observed and documented 20 degrees or more of difference in the nubs we've received -- see https://photos.app.goo.gl/Z44ZH4MamgfWp7S59 and https://photos.app.goo.gl/B4r9DhbXMSW5KRJfA for examples.

At $10 each these are way overpriced for the inconsistent quality of parts received. If used to mount a single round component such as a wheel or gear, they may be okay, but if any sort of alignment is needed, look elsewhere.

I felt like giving these nubs only one star, but we have successfully used them before in another application so they get a point for that.

'The team love the D shaft nubs! One quick question - they found it difficult to thread a #6-32 socket head screw (1/2' long). Rather they used a smaller screw (metric) with a nut. Seems to work fine. So, the team's asking - should they really spend the time to thread the #-32's (16 of them)?'