I like the idea, but I've bought nice rings (singles) that don't fit over the rod. Seems the only way to be sure is to get those big round plastic "O" rings that aren't very pretty.

Is this for a liner and a fabric curtain? Every one I've known just uses a regular ring and inserts the ring into each layer's hole. Nothing special.

I have double rings and love them. It drove me nuts to have to unclip and then reclip every ring every time I wanted to wash the curtain or change or wash the liner.

These are the ones I have. I like them because they're quiet when you open and close the curtain.

Here is a link that might be useful: Aquarius double hook shower curtain hooks.

I have the Moen and it makes life easier. There is a slight noise when you slide them.

I just have one curtain, but I do enjoy the soft whoosh of the ball bearings sliding along the rod.

I have a heavy cotton Matelasse curtain plus a much lighter fabric liner in our master bath. I can't picture how double rings like that could possibly hang straight with the two curtains being different weights. I use plain roller rings in there and love them for the ease of opening and closing my heavy curtain.