Thanks @Bluey! I have actually been trying lots of different bits with my mare. We have the tranz-angled model from your 3rd link in loose-ring, part of her regular rotation. She accepts it well, has seemed to like loose ring best. She was in a Tom Thumb at her last place so anything double-jointed and non-curb is a relief.
I’m looking for a D-ring now for steering issues that show up when hacking narrow curvy tree-lined trails and especially down steep hills. After reading the descriptions on some Sprenger bits I’ve gotten a clearer picture of the action of curved double-jointed lozenge vs. straight double-jointed lozenge.
Your first 2 links, btw, are to the same item. That one looks like NS’ version called “Hunter” - with the straighter joining pieces. Smartpack doesn’t show the diameter, which would be 16mm if it is the Hunter. (Smartpak also doesn’t carry large enough width).
I would have bought the Sprenger KK Ultra but they’re sizing system doesn’t work for us. And I question the quality as the one I received from Dover had pitting in the inner rings - making them rough.
Was reading the descriptions of Fager bits at BitsofBritain site. Someone here was asking about them. They have even better descriptions for how the various shaped double-jointed snaffles act on the tongue and bars. Some put more pressure on the tongue and off the bars. Others more on the bars, and in the case of a fixed cheek, the poll. Each action has it’s use for particular horse behavior. We want more on the tongue, less on the bars/poll.