The eeWings arms are Grade 9 Ti-3AI-2.5V, the hirth joint/chain ring interface, spindle, pedal inserts, fastening bolt and washer, preload bolt, and the three chainring bolts are Grade 5 Ti-6AI-4V Titanium. The 1.75mm spindle spacer, and preload assembly (thread ring and spacer ring) are made of 7075 aluminum.