MusicNomad's 2-Pack String Fuel Refill bottle is designed to refuel the String Fuel Applicator (model # MN109 and MN145, sold separately) once the applicator becomes dry over a period of time due to usage. String Fuel is a hybrid blend of refined naturally occurring oils that are speed blended with premium quality mineral oils to deliver a string cleaner and lubricant unlike any other. The proprietary formulation allows you to both clean and protect your strings, making them last longer and sound better while reducing finger noise and enhancing the speed you can slide your fingers. It is silicone free and safe for any finish, and it even conditions unfinished fretboard wood. Each bottle can refuel the String Fuel Applicator a minimum of two times. MusicNomad products are used worldwide by musicians, repair shops, collectors, and instrument makers.