Bore: C (Standard) Material: N (Soft German Silver - Standard) Plating: Silver Plated Length: 1 (442Hz) Metal Thickness: 0.6mm (Standard) https://heckel.de/wp-content/uploads/2018/08/Wilhelm-Heckel-GmbH-S-Boegen.pdf This is a used item purchased from a professional musician. It has a moderate to slightly heavy blowing resistance. The material letter is slightly smudged, but according to the seller, it was like that from the time of manufacture, so there shouldn't be any particular problems.