This is only the underpart of the flugelhorn mouthpiece from the popular manufacturer AR Resonance. The S backbore is a relatively tight backbore, allowing for a compact flugelhorn sound. I used to select this backbore when playing in a big band. - Model Name: AR Resource - Material: Raw Brass The top part is also listed separately, so please consider purchasing it together. I am open to price negotiations, so feel free to contact me.