Thickness of the chain: 1.2 mm
The length shown is the shortest chain. The longer chain is 0.5cm longer for a nice pendant.
How do I choose my chain length? Measure the distance from piercing to piercing. You can either do this with a tape measure or a string and mark the beginning of one piercing and the second piercing. Measure the distance between the marks with a ruler while you have the string laid flat.
Blackline® is colored jewelry, they are not "colored" in the classic sense, in this case it is Silver that is covered with a thin plasma film (PVD coating). The thin film is very strong and does not fade. The technology has been used in the medical industry since the late 80's and is used, among other things, for pacemakers and orthopedic implants to provide an extra durable surface.