Yamaha"s Air-Seal System shell ensures a perfectly round shell for a lifetimeA 45-degree bearing edgeAir-Seal System hoop provide accurate tuningLug casings reinforced with a zinc, die-cast construction for high-tension tuningNylon and steel washers to minimize frictionA 9-ply Birch shell for a lightweight designSteel claw hooks with a solid rib design to ensure shape retention and eliminate excess stressSound Impact Strips eliminate unwanted overtones and produce a clear tone