A waterproof servo keeps steering when the run gets wet. The 20KG servo at $53.99 suits 1:10 and 1:8 rigs. The metal gear servo at $49.99 spans 20 to 40 kg across 14 models, with 180 or 270 degree travel. The Perfex KS-201 at $8.60 suits light duty, with 3 to 4.5 kg per cm of torque.
What makes a servo waterproof?
A waterproof servo seals its case, so mud, rain, and snow stay out of the gears and electronics.
The 20KG servo listing states a sealed waterproof case in standard size.
A sealed case suits steering on 1:10 and 1:8 rigs, rudders, and any job that gets wet.
20 kg or 20 to 40 kg?
The 20KG servo gives a fixed 20 kg of torque in a standard size case.
The metal gear servo spans 20 to 40 kg across 14 models, so you pick the torque for the rig.
Both servos use a 25T spline output, so the same servo arms fit either one.
180 or 270 degrees?
The metal gear range offers 180 or 270 degree rotation, so you pick the travel for the job.
A 180 degree servo suits steering, while a 270 degree servo suits a winch or a wide-travel linkage.
The metal gear servo measures 40.0 x 20.5 x 40.5 mm and weighs 58 g.
Where does the Perfex KS-201 fit?
The Perfex KS-201 suits light duty, with 3 to 4.5 kg per cm of torque.
It measures 40.5 x 20 x 36.5 mm and weighs 42 g, so it stays light on the build.
Pick it for a small plane or car where a full waterproof servo is more than the job needs.
What did we check on the bench?
We matched the 20 kg torque and the 25T spline to the 20KG servo listing.
We matched the 14 models, the 180 and 270 degree options, and the 58 g weight to the metal gear servo listing.
We matched the 3 to 4.5 kg per cm torque and the 42 g weight to the Perfex KS-201 listing.
Quick comparison
| Servo | Torque | Rotation | Size | Price |
|---|---|---|---|---|
| 20KG waterproof | 20 kg | Not stated | 40x20x38 mm | $53.99 |
| Metal gear range | 20-40 kg | 180 or 270 deg | 40.0×20.5×40.5 mm | $49.99 |
| Perfex KS-201 | 3-4.5 kg/cm | Not stated | 40.5x20x36.5 mm | $8.60 |
Steps
- Pick the torque and rotation for the job.
- Fit the servo in the mount and check the spline lines up.
- Fit a 25T servo arm to the spline.
- Center the servo with your radio before you link it up.
- Test the full travel by hand before you run the model.
Frequently asked questions
Is the Perfex KS-201 waterproof?
No. The listing does not state a sealed case. Pick the 20KG servo at $53.99 or the metal gear servo at $49.99 for wet runs.
What does 25T mean?
It means the output spline has 25 teeth. Fit a 25T servo arm to it.
Can I use a waterproof servo in a plane?
Yes, when the size and torque fit. The 20KG servo suits rudders and any job that gets wet.
How do I pick between 180 and 270 degrees?
Pick 180 degrees for steering and 270 degrees for a winch or a wide-travel linkage.
Parts used
20KG Waterproof Digital Servo, $53.99
Waterproof Digital Servo, 20-40kg, Metal Gear, 180 / 270 Degree, $49.99
Perfex KS-201 Standard Servo, $8.60
JR/Futaba to JST Switch Connector, 2 and 3 Wire, $6.99
Related buying guides on Quality RC Parts
How to Choose a Waterproof Servo for RC Cars and Boats
How to Choose Servos for Your RC Car or Truck
How to Choose Servos for RC Planes and Cars
Browse all the guides on the Quality RC Parts Drone Guides hub, or start at the Quality RC Parts store.
Sources
Quality RC Parts stocks parts in New York, USA and ships in-stock orders in 1-2 business days.
Last updated: 2026-11-11.