Colors on pictures might differ slightly from what you see in real life. This is due to different lighting, different computer monitor settings and my lack of photography skills.
Stainless Steel Hardware
Everything, except rivets, will be stainless. Rivets are nickel coated brass. I don't think stainless snap rivets exist.
Rivets on 3/8" wide products
3/8" wide BioThane shouldn't be riveted. Since it's not that wide, a hole made for the rivet makes a pretty big impact on the integrity of the material. So, 3/8" wide products won't be riveted even if they might be on pictures.
BioThane is pretty amazing. It's basically a strong a polyester webbing with a TPU or PVC coating that makes it more durable, waterproof, easy to clean and it also makes it look and feel like leather.
In my opinion, BioThane has some advantages over leather: it doesn't need maintenance, doesn't stretch when wet, can take lots of abuse and still look new after a wipe. It doesn't keep smells in, it is easily cleanable because dirt barely sticks to it: it really doesn't need cleaning at all, whatever might stick to it will fall off after it dries.
It's also strong, lightweight and flexible. It doesnt tangle easily, doesnt catch on to tree stumps or sticks when dragging on the ground in wooded areas, so this makes it a #1 choice for using it for long lines, tracking lines, search & rescue gear, hiking dog gear, etc.
To sum up, this is a material for pretty much any task and any weather.
You can read all about BioThane on their website. I use Beta 520 in 3/8", 1/2" and 3/4" widths (B10 standard. 3/8" has a tensile break strength of 375lbs, 1/2" has a tensile break strength of 500lbs, 3/4" has a tensile break strength of 750lbs).