Everything Grumbacher makes is tested again and again at every stage of its existence, which inspired the name Grumbacher Pre-Tested Oil Paints. Grumbacher's time-proven formulas are finely tuned through independent laboratory tests as well as hands-on trials by professional artists. They specify the best ingredients available, putting each one through a rigorous selection process. On the factory floor, they sample batches in process and sample the raw material again before shipping their products. And finally, even after their products are in the field, they continue to track batches and test for quality, performance and shelf life. Grumbacher Pre-Tested Oil Paints are the product that represents the way they do business: with care, precision, and attention to detail. On a more specific level, it means simply the finest pigments the world can offer, milled in select alkali-refined linseed oil for the professional artist. These are Grumbacher Pre-Tested Oil Paints in 150ml tubes.