The standard says; Long, thick at root, tapering and reaching almost to the ground. When standing dropped perfectly straight down or curved. Curved when moving, never liften above the line of the back. Well covered with hair; on ipper side thick and wiry, on under side longer, and towards end a slight fringe is not objectionable. A curl or ring tail is undesirable.
It is self explanatory and below is a selection of tails you will see , we aim for the standard but sometimes we fall foul of our inherited genes.