Very thin leather. Tried to use it as an extra "keeper" on one of my SBL bags, and it broke in just a few weeks. I wouldn't care if it was like $5, but for $12, you'd think it would last longer than a cheap rubber band.
These rings can serve multiple purposes, from a cute fashion accessory for the leather lover, but can also help hold the end of a strap down on your favourite Saddleback or Love 41 bag. I use the tobacco one for just this purpose on my Love 41 Rawhide bag and it is holding up well.
The leather has been thinned down quite a bit, I'm not sure how well it will last the 100 years, but the warranty is great and I am not too concerned.
Would love to see these in a wider width as well.