For piston valves with greater-than-average clearance. Hetman Classic Piston Lubricant 3 is valve oil for piston valves with greater-than-average clearanceAll Hetman Musical Instrument Lubricants offer superior lubricating qualities, are longer-lasting than other lubricants, and are completely compatible with conventional petroleum-based lubricants, thereby avoiding potential gumming problems. The viscosity of each lubricant is carefully formulated for its specific purpose and assures both fast, positive action and vital protection against wear and corrosion..