Schleich Farm Animals are all in the same relative scale, roughly 1/18 to 1/24. They are compatible with the Schleich Armies and Horses.

Schleich is a company based in Germany that specializes in the highest quality hand painted models. Created from a tough flexible plastic, this product line is durable enough for vigorous child play. The horses will survive a gallop up the driveway with their legs intact, and the wild animals can fight, roam through the backyard, and emerge unscathed from bath time. The meticulous level of detail pleases adult collectors.
A bit of acrylic paint can customize any of the product line to suit your personal taste, or match a coat of arms.

Products from Schleich include:

Historic armies from the World of Knights, and the American Frontier in 1/18th scale (90mm)
Farm Animals and Wildlife in 1/20-1/24th scale (G scale for model railroaders)
Dogs and cats in 1/12th (doll house scale)
Dinosaurs in 1/40 scale
Ancient Mammals in 1/20 scale
Most of the animals are rated safe for children 3 years old and up.