The KST X20-7.4-M-820 Brushless HLS 6BB Servo is a high-torque HV servo for RC helicopter control positions. KST lists it as a brushless, contactless, hardened-steel-gear servo with a full CNC aluminum case. Verified KST data lists 30Kgf.cm stalling torque at 7.4V, 0.09sec/60deg no-load speed at 7.4V, and a DC 6.0V-8.4V operating range. The servo uses a 1520us/333Hz command format, 25T 6mm spline, and 6 ball bearings. The 40 x 20 x 40mm case and 75g listed weight place it in KST's 20mm-class X20 HLS family for builders who need a robust HV servo with contactless feedback. Product Images Features 30Kgf.cm stalling torque - Listed stalling torque is 30Kgf.cm at 7.4V. 0.09sec no-load speed - Listed no-load speed is 0.09sec/60deg at 7.4V. HV 6.0V-8.4V range - Works with compatible HV receiver and BEC systems. Brushless DC motor - Supports efficient output for high-load control positions. HLS hardened steel gears - Built for durability in demanding RC helicopter use. Contactless position sensor - Improves repeatability and reduces mechanical feedback wear. 6BB construction - Six ball bearings support gear train stability. CNC aluminum case - Provides a rigid 20mm-class enclosure. 25T 6mm spline - Uses the listed output shaft spline. 200deg default travel range - Listed default travel is +/-100deg when commanded from 500us to 2500us. Specifications Parameter Value Model KST X20-7.4-M-820 Shopify SKU KST-X20-74M820 Rated Voltage DC7.4V Voltage Range DC6.0V-8.4V Stalling Torque 30Kgf.cm @ 7.4V Rated Torque 7Kgf.cm @ 7.4V Stalling Current 4.95A Rated Current 1.25A No-load Speed 0.09sec/60deg @ 7.4V Rated Speed 0.17sec/60deg @ 7.4V Working Frequency 1520us / 333Hz Default Travel Angle +/-100deg = 200deg total when 500us-2500us Output Shaft Spline 25T, 6mm Case Material Aluminum alloy Motor Type Brushless DC motor Gear Set Material Hardened steel / HLS Position Sensor Contactless Ball Bearing 6BB Case Dimensions 40 x 20 x 40mm +/-0.2mm Weight 75g +/-10% Temperature Range -10C to +65C Reference Documents KST X20-7.4-M-820 Technical Specification Application RC helicopter cyclic or standard servo positions - Use where the 1520us/333Hz format and servo size match the build. RC helicopter control systems - Supports compatible helicopter builds after confirming servo size, spline, voltage, and signal format. High-load swash or tail setups - Useful where the selected servo type matches the helicopter control position. HV receiver systems - Works within the listed voltage range when the receiver, BEC, and controller are configured correctly. Precision linkage testing - Suitable for setup work where neutral position, travel, and linkage geometry must be verified. Custom PWM motion projects - Can be used outside RC helicopters when load, voltage, duty cycle, and cooling are validated. Packing List Description Quantity KST X20-7.4-M-820 standard servo 1 Accessory pack 1 FAQ .faq-accordion details { border-bottom: 1px solid #e6eef8; padding: 14px 0; } .faq-accordion summary { list-style: none; cursor: pointer; font-size: 16px; font-weight: 700; color: #1f2933; position: relative; padding-right: 32px; } .faq-accordion summary::-webkit-details-marker { display: none; } .faq-accordion summary::after { content: "\203A"; position: absolute; right: 4px; top: 50%; transform: translateY(-50%) rotate(90deg); color: #007fff; font-size: 28px; line-height: 1; transition: transform 0.2s ease; } .faq-accordion details[open] summary::after { transform: translateY(-50%) rotate(270deg); } .faq-accordion p { margin: 12px 0 0; color: #4b5563; line-height: 1.65; } How does X20-7.4-M-820 compare with X20-7.4-M-830? X20-7.4-M-820 is listed at 30Kgf.cm and 0.09sec/60deg at 7.4V. X20-7.4-M-830 is listed at 38Kgf.cm and 0.13sec/60deg at 7.4V, so it trades higher torque for slower listed speed. Does OpenELAB list multiple Shopify variants for this product? No. The current Shopify product is a single variant with SKU KST-X20-74M820. What is the maximum listed torque? KST lists 30Kgf.cm stalling torque at 7.4V. What is the listed no-load speed? The listed no-load speed is 0.09sec/60deg at 7.4V. Is it a tail servo? No. It uses a standard 1520us/333Hz command format, unlike tail servos such as X20-7.4-M-805 that use 760us/560Hz. What spline does it use? The technical PDF lists a 25T, 6mm output shaft spline. What is included in the package? KST lists one X20-7.4-M-820 standard servo and one accessory pack. What should I check before installation? Confirm DC6.0V-8.4V power, 1520us/333Hz signal, 25T 6mm spline, case dimensions, and linkage clearance.
