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Technical Specifications
Last Updated: 2026-10-22| Identity | |
| Brand |  |
| Product Number | KST-0021 |
| Category | Hobby |
| Performance | |
| Torque |
8.4V
38.89 oz-in
2.80 kg-cm
0.3 N-m
7.4V
37.50 oz-in
2.70 kg-cm
0.3 N-m
6.0V
30.56 oz-in
2.20 kg-cm
0.2 N-m
3.8V
19.45 oz-in
1.40 kg-cm
0.1 N-m
Below Average
|
| Speed |
8.4V
0.09 sec/60°
666.7 deg/s
111.1 RPM
7.4V
0.12 sec/60°
500.0 deg/s
83.3 RPM
6.0V
0.15 sec/60°
400.0 deg/s
66.7 RPM
3.8V
0.18 sec/60°
333.3 deg/s
55.6 RPM
Bottom 10%
|
| Physical | |
| Weight | 0.28 oz8.0 gAbove Average |
| Dimensions |
L 0.925 in W 0.315 in H 0.661 in L 23.5 mm W 8.0 mm H 16.8 mm |
| Case Material | Aluminum |
| Drivetrain | |
| Motor Type | Coreless |
| Gears | Steel |
| Gear Spline/Teeth | 15 T |
| Rotation/Support | Dual Bearings |
| Control & Signal | |
| Modulation | Digital |
| Rotational Range | 120° |
| Pulse Cycle | 3.003 ms |
| Pulse Width | 1000-2000 µs |
| Neutral Position | 1520 µs |
| Refresh Rate | 333 Hz |
| Angle Sensor | Potentiometer |
| Control System | PWM |
| Programmable | Yes |
| Signal Voltage | 3.3–5V |
| Electrical & Environment | |
| Operating Voltage | 3.8–8.4 V |
| Temperature | -10–65 °C14–149 °F |
| Connectivity | |
| Connector | JR (Universal) estimate |
| Wire Length | 160 mm6.3 in |
| Origin | |
| Country of Origin | China |
Disclaimer: Most data is sourced from the manufacturer. Some data is sourced from our loyal community and with the help of AI. We aim for accuracy but are not responsible for inaccurate information.
Class Comparison
| Torque | Below Average Stronger than 24% of 349 Digital Micro servos at 3.8V |
| Speed | Bottom 10% Faster than 8% of 347 Digital Micro servos at 3.8V |
| Weight | Above Average Lighter than 75% of 597 Digital Micro servos |
Performance Analysis
| Shaft Power | 0.20–0.80 W |
| Power Density | 4.145 W/in³ More power-dense than 73% of 563 Digital Micro servos |
| Torque Density | 2.4313 oz-in/g Stronger than 49% of 349 Digital Micro servos |
| Torque-to-Volume Ratio | 100.90 oz-in/in³ Denser torque than 72% of 345 Digital Micro servos |
| Speed-to-Weight | 0.69444 (1/sec·g) Faster than 46% of 347 Digital Micro servos |
| Speed-Torque Trade-off | 3.50 Better balanced than 56% of 345 Digital Micro servos |
| Torque Gain per Volt | 21.73%/V More voltage-responsive (torque) than 78% of 290 Digital Micro servos |
| Speed Gain per Volt | 21.75%/V More voltage-responsive (speed) than 74% of 295 Digital Micro servos |
| Voltage Range Width | 4.6 V Wider voltage range than 95% of 496 Digital Micro servos |
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Reviews (8)
Includes 8 reviews aggregated from around the web.
There are few reviews for this servo on the web. A glider retailer's listing averages 5.0 out of 5 from 5 ratings, with no written details. Forum glider pilots use it in tail and wing positions and one praises its centering accuracy, though he recommends a cheaper FrSky servo as an alternative with telemetry. A reminder from the same poster is to calibrate your sticks, since factory calibration is not perfect. No failures were reported.
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