A Rex rat has a curly or wavy coat, including the whiskers. Rex whiskers can range from drooping, curled ends, or even a mad frizz. The coat itself should not be frizzy and should have a plush, thick feel to it. Many Rex rats go bald in patches, especially the upper back, when moulting or in old age; a more desirable Rex keeps their full coat their entire life.

A rat's curl often relaxes the older they get, thus a very tightly curled baby Rex will often look simply wavy or frizzy when they are elderly.

Rex is a heterozygous dominant gene. That means that a single dominant gene will cause the rat's fur to curl, as will a double dominant. That means Rexing cannot "carry" - breeding two standard coat rats together will never produce a Rex.

There has been discussion over the last decade or more about different Rexing genes, such as "Curly" and "Wavy" and "Double Rex" - however, it has not been proven. Some say that a double-dominant Rex turns out to be a "doublerex," meaning the rat have very short, sparse curly hair which moults in odd, changing balding patterns. However, that may simply be poor breeding selection for a thinner, more moult-prone coat. Since doublerexing is not standardized, and is not a high-quality coat, it is doubtful anyone will undertake to prove the point.

AFRMA

"The coat to be evenly dense and not excessively harsh, with as few guard hairs as possible. Coat to be evenly curled and also to a lesser extent on the belly. Curly vibrissae (whiskers) are normal for Rex. Color to conform to a recognized color or pattern."

RSA

"Coat to be tight even waves or curls. Eyebrows and whiskers to show definite curl. Faults: frizziness, lack of wave/curl, straight whiskers, bald spots."

RatsPacNW

Rex

"Curly coat & whiskers.  Coat should be even and dense but may thin with age.  Texture will feel rougher than a velveteen."

Velveteen

"Wavy coat & softly curled/wavy whiskers.  Coat should be even and preferably dense.  Older rats coats may thin with age and this is a fault for show.  Texture to be soft."

Double Rex

"Mock hairless or patchwork hair.  Must be a standardized color and marking.

  Patches should be random, whiskers curled."

URS

Rex

"Fur to be thick and densely curled. Guard hairs should be coarse and easily felt. Whiskers to be curled.

Faults: Frizzed, loose coat, bald patches."

Double Rex

"Several variations may appear on the table. Bald patches among short, wirey coat that resembles that of a poodle or partially sheared lamb. A rat nearly bald with small areas of 'peach fuzz' on the muzzle, legs, and base of tail. A very short, wirey coat that looks similar to a 'buzz cut'. Whiskers and eyelashes should be curled. Faults: Fully furred with hair that is too long or soft and resembling a standard coat, or one that is fully furred with medium-length, wirey coat resembling a regular rex."

Cinnamon Rex (c) Kirstin Allan