Getting the proper pigment is just the beginning! So much of the quality of oil paint is in the grinding. Each color is ground to enhance the beauty and luminosity specific to that particular pigment. Pigments are ground in pure alkali-refined, ph balanced linseed oil, and made in batches no larger than 5 gallons at a time. All materials are hand measured, and every ounce of paint is scrutinized. Gray color set includes N2, N4, N6 and N8. Details: Includes neutral gray colors 37 mL tubes 4-color set Ground in pure alkali-refined, ph balanced linseed oil Hand measured, made in batches no larger than 5 gallons High-quality oil paint