Black leather, stainless steel buckles and rings. It's one of the most popular designs, but this one has many custom features.
A few studio pics:
A - Throatlatches are 3/4" wide instead on usuals 1/2".
B - Crownpiece is made with doubled Sedgwick leather, stitched together using 10 meters of waxed linen thread.
C - Noseband is the most special: I've used nylon strap instead of leather for holding rings in place, for keeping thickness as low as possible. There's also a stainless steel ring stitched next to the buckle.
D - Last but not least, browband with Swarovski crystals. I bought them a couple of years ago but this is the first time I use them.