I had to modify this with some gentle bending on a vise to get it to work on a Reiter banjo with a 12 inch pot, I think that the radius is probably designed for an 11 inch pot but it's working well after modifying.
good value.

This is as well made Asian copy of the type of armrest used by the Vega company. Vega banjos had 24 to 28 brackets and varied pot sizes from about 10 1/2 inches to almost 12 inches in diameter. In contrast to the Mastertone type of armrest for a bluegrass banjo which clamps to the hooks and depends on a specific spacing between two hooks to fit right, this armrest is held in place by hooks which run through slots on the side of the armrest and presses it against the side of the stretcher band. It is specifically designed this way in order to accommodate various bracket spacing so I am a little puzzled by the reviewers who have had trouble attaching it to their banjos. The armrest is relatively small and just keeps your arm off the head rather than providing a flat landing for your forearm, so some might find it less comfortable. However I have used it on several types of open-back banjos (Vega tubaphones and a Bacon FF banjo) without having to modify the armrest or attach it to the banjo by anything other than a pair of appropriately spaced hooks.

I used it on my SS Stewart American Princess banjo and it fit perfectly. I uses plastic ties to attach to banjo head. Inexpensive and effective. I recommend this product.

I put this on an old style banjo, it keeps my arm off the head. Glad I bought it.

Fits perfect on my 18 hook old time banjo.