Coiled tubing or a portion thereof having a first part spaced-apart from a second part, the coiled tubing having a first outer diamter at the first part and a second outer diameter at the second part, the first outer diameter different from the second outer diameter, and outer diameter of the coiled tubing continuously diminishing or increasing from the first part to the second part, in one particular aspect thus varying over its entire length; and methods for using and methods and apparatuses for making such coiled tubing.