Want a small FPV drone with the DJI O4 Pro that is fast and agile? Then you have to check out the Flywoo Firefly 20 Pro. Not only does it fly really well, it also has one of the simplest yet most practical designs I’ve seen in a micro quad.
Check out my review of the Flywoo Firefly25: https://oscarliang.com/flywoo-firefly-25-mini/
Where to Buy
Get the Firefly 20 Pro from:
In the box it comes with these accessories.
Specifications
- Designed for DJI O4 Pro Air Unit
- FC / ESC Board: GOKU F405 SE 20A AIO
- Gyroscope: ICM-42688-P
- Flash Memory for Blackbox: 8MB
- Receiver: Flywoo EL24E ExpressLRS 2.4GHz
- Motors: ROBO 1303 6000KV
- Propellers: Gemfan 2023-3 3-Blade, 1.5mm shaft
- Battery Connector: XT30
- Recommended Battery: 4S 550mAh / 750mAh LiHV
- Claimed Flight Times
- 750mAh: 6 min 30 s
- 550mAh: 5 min
- Claimed Max Speed: 120km/h
- Weight (excluding battery): 112.5g
Design and Build Quality
It’s one of the smallest quads designed for the full-size DJI O4 Pro. It’s not the smallest though — that title still belongs to the WalleFPV Eagle2. However, the flight performance is not really comparable. The Firefly 20 Pro handles much better: it is more agile, more powerful, and also more efficient thanks to the larger propellers and bigger motors, just an overall better quad.
A lot of thought clearly went into optimizing the weight. You can see it in details like the ultra-light plastic side panels and battery straps.
Even so, the 2.5mm-thick unibody carbon fibre frame feels pretty strong, probably strong enough to survive a few crashes on soft ground and grass.
It’s also very easy to access the FC USB port, as well as the DJI O4 Pro’s bind button, USB port, and SD card slot.
I really like how simple the design is. There is nothing too fancy or overcomplicated, just very practical. You only need to remove 4 screws to separate the top plate from the quad, giving you access to the O4 Pro air unit and flight controller. That makes it very easy to work on and especially beginner-friendly.
It also has two bright RGB LEDs, one on each side of the drone, integrated into the flight controller, and are customizable in Betaflight.
DJI O4 Pro Mounting
The DJI O4 Pro air unit is mounted under the top plate. The camera is properly soft-mounted to help prevent jello.
Flywoo has replaced the original O4 Pro antennas with two lightweight dipole antennas. This might reduce maximum range, but this quad is really designed for close-range flying, so they should be more than adequate. Even with these simple antennas, the Firefly 20 Pro should still be capable of at least 1–2 km of range, so I would not worry too much about it.
Camera angle is adjustable, though the range is not huge: 0° to 25°. The side panels get in the way of the camera screws, so if you want to adjust the camera angle, you need to remove them first. They are “quick release” panels that simply clip onto the standoffs, so they can be removed easily by hand without taking off the top plate.
No GPS
The lack of GPS on the Firefly 20 Pro means it becomes riskier the farther you fly, especially when it is carrying an expensive DJI O4 Pro. So it is better suited to close-range or indoor flying, where you can still easily retrieve the drone after a crash.
That said, the flight controller has a dedicated port for a GPS module, so installation is easy if you want features like Rescue Mode or Position Hold.
I recently tested quite a few GPS modules, and for a micro drone like the Firefly20, these are some good options:
NewBeeDrone M10Q Micro
FlyFishRC M10 Mini:
Cyclone M10:
Beeper
It’s good to know the Firefly 20 Pro has a physical buzzer located under the flight controller (integrated into the FC itself). It makes a big difference when you crash and lose your drone in tall grass. Micro quads this small do not commonly come with a proper beeper, so you would normally have to rely on the motors beeping through DShot Beacon. But that is usually very quiet, which makes it much harder to find your quad. With a real buzzer, it is much easier to locate the Firefly 20 Pro.
Battery Choices
You can use both 3S and 4S on the Firefly 20 Pro. In fact, 4S is what Flywoo recommends in the specifications. I tested both.
You can purchase the batteries here:
Personally, I prefer 4S because of the extra power. But if you prefer more relaxed cruising, 3S is also a good choice.
Other FPV System?
The Firefly 20 Pro is designed specifically for the DJI O4 Pro, but that does not necessarily mean you cannot use another camera/VTX system in this drone. It would just require some DIY work and possibly a custom camera mount.
Flight Performance
I’m very happy with how it flies. It is ridiculously agile, picks up speed very quickly, and turns on a dime. It is also really quiet for a 4S quad. You can barely hear it from 100 meters away.
It handled wind pretty well too. I was testing it in 16–18 mph winds, and it flew just fine. There were some small vibrations here and there because of the gusts, but you can smooth those out in your footage using Gyroflow in post editing. I did not get any jello at all, which indicates the soft mounting is working well.
I tested it on both 3S and 4S, and the feel is very different.
Obviously, it is much faster and more agile on 4S, but it is also slightly louder. If you are more into smooth cruising and want to maintain a stealthier profile, 3S is a great choice.
Here are the flight times I got with different batteries (a mix of freestyle and cruising):
- 3S 750mAh: 5 minutes
- 3S 1000mAh: 8 minutes
- 4S 720mAh: 6 minutes
When it comes to speed, the Firefly20 was actually faster than what Flywoo claims in the specs. Since it does not have GPS, I had to estimate speed based on the time it took to travel a certain distance at full throttle, so this is not the most accurate figures, but it gives us an idea:
- On 3S, I am getting a top speed of around 110–120 km/h
- On 4S, top speed is around 140–150 km/h
PID and Filter Tuning
The PID and filter settings are tuned at the factory, but in my opinion the tune is pretty conservative and definitely has room for improvement.
It also runs an older version of Betaflight, so before I tuned it, I updated it to the latest version (2025.12.2). If you are already happy with how it flies, I would avoid updating Betaflight because you would have to set everything up again from scratch.
Anyway, I shared my custom PID and filter tune on my Patreon, along with screenshots of all the settings I changed: https://www.patreon.com/posts/custom-pid-tune-155764066
My custom tune is for 4S, but it should also work fine on 3S.
How to Setup For First Flight
Firmware
- The flight controller (FC) board target is FLYWOOF405S_AIO, and it comes preloaded with Betaflight firmware version 4.5.1. For stock CLI Diff, see here.
- ESC Firmware: Bluejay G-H-30, 0.19, 48kHz
- ELRS Receiver Firmware Target: Flywoo EL24E, doesn’t specify what version, but it binds with radio on V3 firmware
- The quad runs props out (motors reversed).
Steps to Setup
- Bind the ELRS receiver (connected to UART3) – Detail tutorial: https://oscarliang.com/bind-expresslrs-receivers/
- In Preset tab, search and load the ExpressLRS preset that matches your packet rate – Instructions: https://oscarliang.com/rc-link-preset-betaflight/
- In PID Tuning tab, set up rates according to your preference – My Rates: https://oscarliang.com/rates/#My-Rates
- In Receiver tab, enable Telemetry. Roll and pitch channels jumps a tiny bit, so setting deadband (both RC and Yaw) to 3 can help prevent jitters
- In Modes tab, setup arm switch, Angle mode, Turtle mode, Beeper, etc.): https://oscarliang.com/betaflight-modes/#How-to-Setup-Arm-Switch
- In OSD tab, under Video Format, select HD. Then setup OSD elements, or you can copy my CLI lines: https://oscarliang.com/betaflight-osd/#My-OSD-Setup-CLI-Commands
- Pair the DJI O4 Air Unit with your goggles (connected to UART6) – Guide: https://oscarliang.com/how-to-setup-dji-o4-pro/#Pairing-DJI-Goggles-3-with-O4-Air-Unit-Pro
- In Power & Battery tab, I lowered Amperage Meter Scale from 170 to 165.
Conclusion
I enjoyed flying this quad, and I love how simple and practical the design is. It is designed for high-speed racing in tight spaces and aggressive freestyle flying, yet it is still small and quiet enough to fly in small local parks without causing as much annoyance as a larger 5-inch quad.
I can definitely recommend it.
Get the Firefly 20 Pro from:
However, there is also a 2.5-inch version, which I will be reviewing later this week. If you are deciding between these two models, you may want to wait for that review for a full comparison: https://oscarliang.com/flywoo-firefly-25-mini/
For now, here is Flywoo’s own explanation of the difference (although I don’t 100% agree 😀 ):
The Firefly20 PRO is built for extreme outdoor racing, high-speed maneuvering, and maximum 4S power bursts.
The Firefly25 MINI is made for long-endurance freestyle, indoor tight-space flight, and smooth aerial shooting.
Both models support seamless swapping of the digital transmission system with just 4 screws.
