Continuing to shake up the increasingly competitive power meter market with the worlds' lightest and most accurate power meters, 4iiii Innovations have launched this great Shimano Ultegra FC-R8000 Left Hand Crank Arm with pre-installed 4iiii Precision Power Meter. Whether you’re a pro, or simply training hard, the PRECISION left side "ride ready" power meter delivers: • Industry-leading accuracy (+/- 1% error margin) • Highly-dependable cadence data • 3D power meter technology capable of measuring tri-axial strain on your crank arm • Waterproof pod construction Designed to be durable and lightweight (just 9 grams in weight) PRECISION helps you train harder and smarter. It is favourably compatible with ANT+ and Bluetooth head units, smartphones, and other 4iiii products. These crank arms will fit bottom brackets using the Hollowtech II interface.