Using nuts as spinlock for barbell.

I got these free weights from Walmart. They cheaped out on the material and the end cap which holds the weights to the bar craped out. I am looking at this thing to buy as a replacement. Since Homedepot won't allow people to go into stores, I need to get the measurements correct before I order for curbside purchase.

https://www.homedepot.ca/product/lesso- ... 1000116195

Lesso ABS DWV 1-1/2 Trap Adapter Hub x SJ -> is the 1-1/2 referring to the diameter inside the ring or outside of the ring?

I am thinking of buying these from homedepot as opposed to these from walmart cause of the price difference: https://www.walmart.ca/en/ip/1-25mm-Sta ... TVVQ18QVU9