The specification for kidney beans can vary depending on the country of origin and the customer's requirements. However, the following is a general specification for kidney beans:

1. Size: The size of kidney beans can range from small to large, but the most common size is around 0.5 to 0.7 inches in length.

2. Shape: As the name suggests, kidney beans have a kidney-shaped structure.

3. Color: Kidney beans are typically reddish-brown, although they can also be white, black, or mottled.

4. Moisture content: The moisture content of kidney beans should be below 14% to prevent spoilage.

5. Impurities: The beans should be free of foreign matter, such as stones, dirt, or other debris.

6. Packing: Kidney beans can be packed in various sizes of bags or containers, depending on the customer's preference.

7. Storage conditions: Kidney beans should be stored in cool and dry conditions to prevent moisture buildup, which can cause mold or fungus growth.

Overall, kidney beans are a popular legume due to their high nutritional value and versatility in cooking. They are used in various dishes, such as chili, salads, and soups.