Number 1: Soft - This is an extremely pliable clay used for making large sculptures. It is easily scraped from molds.
Number 2: Medium - This is the choice for portrait heads, busts, and figure work. It is stronger than Number 1: but works smoothly and is the favored consistency.
Number 3: Medium Firm - This is a firmer grade of plastalina used in making models of smaller objects.
Number 4: Extra Hard - This grade of plastalina is used in making extremely detailed objects with great detail such as medallions.
Plastalina (or plasticine) is an oil-based, non-hardening modeling compound. Because it contains wax instead of water, plastalina remains pliable and can be used over and over again. It is smooth and does not stick to the hands and fingers, unless it is very warm. Our clay is made by combining various waxes with different properties---ranging from soft to hard and from plastic to brittle---and melting them until well blended in a steel vat. A powdered filler and pigments are added to the melted wax and then mixed together to form a finished product.
Read more about how to use non drying clays here.