Quick Answer
The HappyModel Mobula8 O4 is a 50g, 85mm 2S whoop with a built-in DJI O4 Air Unit, ExpressLRS 2.4GHz receiver, and EX1103 11000KV motors. It is the lightest ready-to-fly DJI O4 whoop we stock, sitting below both the BetaFPV Meteor75 Pro II O4 (100g) and the Flywoo Flylens 85 O4 (75g). If you want DJI O4 HD video in the smallest package that still flies properly on 2S, this is it.
Why the Mobula8 O4 Exists
The DJI O4 Air Unit is the current standard for HD FPV, but it is physically large and power-hungry. Shoving it into a 75mm frame meant either flying 1S (not enough headroom for outdoor freestyle) or accepting a heavy quad that flies like a brick. HappyModel went a different route: an 85mm wheelbase gives enough prop authority to carry the O4 weight on 2S, while the CrazyF405HD AIO keeps the electronics stack compact. The result is a 50g quad that still rips.
What separates the stock Mobula8 O4 BNF from every other O4 whoop is the included FOV extender lens kit. The stock DJI O4 camera has a notoriously narrow field of view. HappyModel ships a wide-angle adapter and ND filters in the box, widening the FOV to roughly 150 degrees. That is the difference between feeling like you are looking through a toilet roll tube and actually seeing the gap you are about to fly through.
Specs That Actually Matter
| Spec | Mobula8 O4 |
|---|---|
| Wheelbase | 85mm |
| AUW (with O4) | 50g (no battery) |
| Flight Controller | CrazyF405HD (STM32F405, BMI270) |
| ESC | 12A 4-in-1 BLHeli_S (Bluejay 0.19) |
| Motors | EX1103 11000KV |
| Props | Gemfan Hurricane 2023 (52mm, 2.3" pitch) |
| Receiver | Built-in ExpressLRS 2.4GHz (UART, not SPI) |
| Battery | 2S 450-550mAh LiHV (XT30) |
| Video | DJI O4 Air Unit (1080p 100fps) + FOV extender |
The built-in ELRS is UART-based, not SPI. That matters because UART receivers support higher packet rates (150Hz) and longer range than SPI modules. You are not making a link compromise to save weight. We pair ours with a RadioMaster Pocket Crush for indoor sessions.
The Weight Reality Check
That 50g figure is without a battery. Add a 2S 550mAh LiHV (like the BetaFPV LAVA II 2S 580mAh) and you are at roughly 70-75g all-up. Still lighter than the Meteor75 Pro II O4 at 100g AUW.
Under UK rules effective January 2026, the Operator ID threshold dropped from 250g to 100g for camera-equipped drones. At 70-75g all-up the Mobula8 slides under that line, but if you add an action camera mount or heavier pack, you could push over 100g. Check your registration requirements carefully.
Mobula8 O4 vs the Competition
The closest alternative in our ready-to-fly collection is the Flywoo Flylens 85 O4 at 75g AUW. Both are 85mm 2S O4 whoops. The Flywoo has replaceable arms for durability, but the Mobula8 is 25g lighter and the FOV extender gives better situational awareness. Our take: Mobula8 for indoor ripping, Flylens 85 if you crash a lot while learning.
For comparison with BetaFPV's O4 options, see our Meteor75 Pro O4 review and Flywoo Flylens 85 review.
What We Would Actually Buy
For indoor UK flying where you need DJI O4 HD in the smallest possible footprint, the Mobula8 O4 is our pick. It pairs with DJI Goggles N3 and any ELRS radio. Grab 2-3 packs of 2S 450-550mAh LiHV because at this power level you will want spares. If you want the absolute lightest O4 option and accept 1S limitations, the BetaFPV Pavo Femto O4 at 84g is worth a look.
FAQ
Q: Do I need DJI goggles for the Mobula8 O4?
Yes. The DJI O4 Air Unit requires DJI goggles. It is not compatible with Walksnail or HDZero. The Goggles N3 are the cheapest compatible option.
Q: Can I fly the Mobula8 O4 on 1S?
Technically yes (supports 1-2S), but we would not recommend it. The O4 Air Unit draws significant power and 1S cannot maintain voltage under load. You will get voltage sag and brownouts. Use 2S 450-550mAh.
Q: Do I need to register the Mobula8 O4 in the UK?
At roughly 70-75g all-up with a 2S battery, it sits under the 100g Operator ID threshold that took effect in January 2026. But check your exact AUW: accessories or heavier batteries may push you over.
Q: What radio do I need?
Any 2.4GHz ELRS radio. The built-in receiver is ExpressLRS 2.4GHz (UART, not SPI). RadioMaster Pocket Crush, Boxer, or TX16S all pair well.
Q: Can I fly it outdoors?
Yes, on 2S it has thrust for light wind. The 85mm wheelbase and EX1103 motors give enough authority for backyard freestyle and park flying. It is not a long-range or windy-conditions quad.