Adult female rats typically weigh 12 to 16 ounces (350 to 450 g), and adult male rats usually weigh 16 to 23 ounces (450 to 650 g) ( see Table: Rats at a Glance Rats at a Glance ). They are about 9 to 11 inches long without the tail. Male rats are usually larger than females. Pet rats are available in several colors and coat patterns because of specialized breeding. The common color variations include brown, black, tan, gray, and white, with both lighter and darker shades as well. Some of the more exotic colors are Siamese, blue, silver black, silver fawn, lilac, cinnamon, black-eyed white, cinnamon pearl, lynx, silver agouti, silver lilac, and blaze. Rex rats have a curly coat. Tailless rats are born with no tails and hairless rats have no fur. The usual life span of rats is about 1.5 to 3 years.