The second-largest category of primary stabilizers after lead salts, metal soaps offer thermal stability slightly inferior to lead salts but provide lubrication. They are typically used in combination with other metal soaps, lead salts, or organotin compounds rather than alone. Except for cadmium (Cd) and lead (Pb), they are non-toxic, and except for lead (Pb) and calcium (Ca), they are transparent and free of sulfur staining. As a result, they are widely used in flexible PVC applications, such as non-toxic and transparent products.