This listing is for a saxophone thumb hook, two types of thumb rests, and a neck protection cap (for soprano saxophones), for a total of four items. These are replacements for when parts are damaged or deteriorated. All materials are plastic. ■ Thumb Hook (for alto and tenor saxophones) 1 piece Length: Approximately 50mm Width: Approximately 20mm ■ Thumb Rests A: Thumb rest in the top of photo 2, 1 piece Outer diameter: Approximately 24mm Thickness: Maximum approximately 9mm, Minimum approximately 7mm Inner diameter of the back: Approximately 14mm ← Diameter of the mounting part on the body side Depth of the back: Minimum approximately 5mm ← Protrusion length of the mounting part on the body side Maximum approximately 7mm B: Thumb rest in the bottom of photo 2, 1 piece Outer diameter: Approximately 23.5mm Thickness: Maximum approximately 10mm, Minimum approximately 8mm Inner diameter of the back: Approximately 14mm ← Diameter of the mounting part on the body side Depth of the back: Minimum approximately 6.6mm ← Protrusion length of the mounting part on the body side Maximum approximately 8.6mm ■ Neck Protection Cap (for soprano saxophone) 1 piece Diameter of insertion part: Approximately 16.6mm Total length: Approximately 22mm Please measure the parts of your instrument and compare them with the sizes above to determine if they are compatible with your saxophone. The user is responsible for determining suitability.