Dun is a common marking that creates a dorsal stripe and leg stripes. At minimum, there must be a dorsal stripe down the back. The maximum heterozygous presentation is a dorsal stripe going down the entire spine, from the back of the head to the tip of the tail, and the thin leg striping can cover a foot-length in maximum size and be placed anywhere on the legs, up to halfway up to the elbows, and halfway up to the knees. 

The stripes must be clumped together and wrap horizontally around the leg. The individual stripes can't be too large, must taper in width, and can't have a perfectly uniform width all around like Rings. 

In homozygous form, the stripes can be wide enough to cover the whole leg range, and there can be vertical stripes around the shoulders and hips.

Dun is allowed to layer over Siamese.