The steel D-840WP is part of our D-Series dynamo servo line. All Hitec D-Series servos have been designed using our brand new, cutting edge, custom engineering. Combining industry leading high-resolution, state-of-the-art ultra-response technology with a 32-bit MCU and 12-bit ADC for unprecedented programmability and flexibility, these servos deliver significantly smoother movement. The speedy, powerful line operates on a wide 4.8 ~ 8.4 voltage range, allowing use with any common battery chemistry without the need for adapters or regulators. Featuring Hate's industry standard 25-tooth output spline with 3mm hex screw, each D-Series servo brings monster performance never known before in the market.