Bio-Rotor Oil Description A Naturally Pure - High Purity Oil, specifically designed for Rotor Valves, which are found on FRENCH HORNS, Rotor Valve TUBAS, GERMAN TRUMPETS and on F-ROTOR TROMBONES. This oil is a tad thicker than trumpet valve oil, which is essential in providing proper lubrication of the rotor within the rotor casing. Summary Medium-to-Thin Viscosity Long Lasting, High Purity Oil Ensures Smooth Rotor Action 30ml (1.01 fl oz) Child Proof Dropper Bottle