In the Shimanos numerous lineup, the "DURA-ACE" model name is Duralumin (Duralumin) and Durabilitys initial meaning for durability, and is called DURA-ACE by combining DURA with "WORLD" "ACE".It weighs 505 grams and is very light. Model Number: FC-7710; Series: DURA-ACE TRACK; Chain Size: 1/2" x 1/8"; P.C.D.: 144mm; Arm Length: 6.5mm/6.75mm/6.75mm/6.75mm/6.77710/BB-7700. Sold separately. Chain Line: 1.7 inches (42.5 mm), BB Length: 4.3 inches (109.5 mm), BB Shell Width: 2.7 inches (68 mm), Weight: 17.0 oz (505 g) (6.7 inches (170 mm).