This keyoil (heavy) is handy for use with Bassoon, Bass Clarinet, Baritone Sax etc. Sometimes rods etc dry out (even before a regular service) a key may "stick" so I keep a bottle of this handy and with a small amount applied can help free up keywork. By keeping rods/pins/screws lubricated you can also avoid unnecessary wear and cost of replacement. Worth having at hand.