The 4mm-thick shell is made of 17 layers of prepreg material (carbon fiber board). All but one of the central layers are aligned in a single direction to maximize vibration damping characteristics. Item: HS-CF Shell: 4.0mm thick CFRP (17-layer prepreg material) Socket: Aluminum coupling with press-fit resin insulation Contact: Gold plated brass Dimensions :L=56mm W=20mm H=15.9mm Accessories: 5N sterling silver shell lead HSR-AG (already attached to HS-CF) Brass screws (two M2.6/ length 7mm, two M2.6/ length 12mm) Brass nuts (two M2.6 size) .