There are only two species of beaver. The American beaver (Castor canadensis) typically weighs 60 lbs. (27 kilograms) and are 23 to 39 inches (60 to 100 centimeters) long. The tail adds another 7.75 to 12 inches (20 to 30.5 cm) to its length.
Eurasian beavers (Castor fiber) are around the same size. They usually weigh from 29 to 77 lbs. (13 to 35 kg) and are 29 to 53 in (73 to 135 cm) in length. Their tails are narrower and skulls are smaller than those of the American beaver.
Bring your own pin and use stealth as there will be beaver muggles galore.