The HG901 11-speed chain from Shimano brings back the dual purpose road / mountain chain at the Dura-Ace and XTR level. This new Ultegra-level design meets the needs of 11-speed mountain groups that require the HG-X11 special asymmetrical design. This streamlines the Shimano chain offerings and makes it simpler for regular road and mountain riders to have spare equipment on hand. Shimano applies it's SIL-TEC plating treatment of carbon and flourine molecules to the HG901. The chemical process bonds to the Pin Link Plate and the Roller Link Plate, which greatly reduces friction and prolongs drivetrain life. Shimano claims a 60% improvement in friction over its nickel plated chains, and 20% greater wear. SIL-TEC also repels water and dirt, allowing your drivetrain to run cleaner and drier through any road or trail conditions. Even if variables reduce those claims by half in real life usage, those are still significant gains. Proper installation is crucial, as the HG901 has a directional design, and employs hollow pins to reduce weight. At 251 grams, this versatile 11 speed chain is competitive with other high-end chains, and with the new SIL-TEC treatment, redefines chain wear for Shimano's premium road and mountain drivetrains.