Titan Highline® is completely nickel-free and is suitable for sensitive and very allergic people. It is half as heavy as steel, and is one of the five substances best accepted by the body. It is not really the titanium itself that is so good for the body but the layer of titanium oxide that forms on the surface. The oxide layer also acts as a barrier against other substances in the titanium leaking into the body. If the titanium oxide surface is worn away, a new layer is formed immediately. We have two different series of Titan; Titan Highline® which is the best quality you can get, it is a highly polished variant of very high quality, and we also sell Titan Basicline® which is a slightly cheaper alternative, it is also completely nickel free but it does not have the same high-gloss finish and can be experienced as darker in color.
Both Surgical Steel and Titanium are basically "silver colored" but are nowadays available in several different colors.
Zirconline® is colored jewelry, they are not "colored" in the classic sense, it is 316L Steel or Titanium 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 since the late 80's and is used, among other things, for orthopedic implants to provide an extra durable surface.