
I haven't used them one's to my knowledge but look similar to ones friends use and they are strong. I have used very thin leather and very thin chains on my setters and never had a lead break. The worst that happends is the stiching on mine have started to come undone but where I got them from stich them back up for free.
Most of my full leather leads have a swivel in them.
Just remember they are only for use in the show ring and training.