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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteSlimeVR Butterfly is the company’s official, prebuilt version of the community “Smol Slime” concept. It uses an IMU for rotation tracking, a split “wing” body built around a Nordic nRF52833 radio, and a dedicated USB receiver instead of Wi‑Fi. The result is a tracker SlimeVR specifies at under 7 mm thick, under 10 g, and up to 48 hours per charge. It is available to order through Crowd Supply, but orders shown on August 18, 2026 listed October 30, 2026 shipping, so it is not yet delivered hardware for most buyers.
What Butterfly actually changes
Butterfly is a full-body-tracking sensor for VRChat, social VR, streaming and motion capture. It does not replace SlimeVR’s underlying tracking method: each unit measures orientation with an IMU, while SlimeVR combines those rotations with headset position and your body proportions to estimate the positions of your hips, legs, feet, chest, elbows or head. It is therefore not an optical positional tracker with independently measured coordinates like a lighthouse or camera system. See SlimeVR’s tracking explanation and the official Butterfly listing.
| # | Preview | Product | Price | |
|---|---|---|---|---|
| 1 |
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1 pc SlimeVR Plus Tracker BNO085 for VRChat SteamVR Body Motion Capture(1 BNO085 Tracker) | $134.00 | Buy on Amazon |
The “Butterfly” name describes the hardware layout. The battery and circuit board sit side by side in two connected halves rather than being stacked in a thick rigid case. A flexible band lets the assembly bend around the body and reduces the pressure point created by a conventional block-shaped tracker. SlimeVR says the design is intended to remain comfortable when sitting or lying on it; that is a manufacturer claim, not an independently measured comfort result.
Size, weight and battery claims
| Specification | Butterfly product-page claim |
|---|---|
| Thickness | Less than 7 mm |
| Weight | Less than 10 g |
| Battery | 90 mAh |
| Runtime | Up to 48 hours |
| Wireless range | More than 10 m under SlimeVR’s stated conditions |
| Radio protocol | Custom 2.4 GHz Enhanced ShockBurst (ESB) |
| Receiver capacity | Up to 10 Butterfly trackers per dongle |
These are specifications and maximum claims from SlimeVR, not independent laboratory measurements. The broader Smol Slime documentation describes typical devices as approximately 10–15 g, 40–60 hours and 7–12 m. Those ranges describe the wider community architecture; the product page gives the more specific Butterfly numbers. Actual runtime and range vary with firmware, radio conditions, battery age and placement.
#1 Best Overall
- The advanced BNO085 sensor delivers drift-free, high-precision motion tracking, enabling realistic full-body avatar motion capture in VRChat and SteamVR.
- Low-latency wireless data transmission ensures real-time synchronization of virtual movements.
- Rugged and durable, featuring secure strap mounts, it can be worn comfortably on the hips, ankles, or wrists.
Why Nordic nRF hardware requires a dongle
Most earlier official SlimeVR trackers send data directly over 2.4 GHz Wi‑Fi. Butterfly and other Smol-style devices use Nordic nRF microcontrollers and a modified ESB link. The tracker transmits to a dedicated receiver, and the receiver forwards the data to SlimeVR Server.
- Less network setup: you do not enter Wi‑Fi credentials for every tracker or depend on the quality of your router.
- Lower tracker power use: the short, purpose-built radio link is designed for small batteries.
- Extra hardware: the dongle must remain connected to the PC, standalone headset or supported Android host.
- Shorter coverage: SlimeVR’s own comparison gives Smol devices less range than Wi‑Fi trackers. A crowded room, walls or a poorly positioned receiver can reduce usable distance.
The Butterfly listing identifies Nordic’s nRF52833 as a key component. SlimeVR’s open repositories cover broader nRF52 and nRF54L tracker support, while the receiver project references nRF52833 and nRF52840 targets. That does not mean every chip in the community ecosystem is inside the production Butterfly. Firmware sources are available in the tracker repository and receiver repository.
Battery and charging in real use
Butterfly uses USB‑C charging and a 90 mAh cell. “Up to 48 hours” is a best-case manufacturer figure, not a guaranteed interval. A multi-tracker setup can still create charging work: ten or seventeen units mean ten or seventeen small batteries to keep ready. The optional dock charges up to ten trackers, but its AC adapter is not included. The trackers can also be charged individually over USB‑C.
Is tracking accuracy better?
There is no published independent test establishing that Butterfly is more accurate than older official Wi‑Fi SlimeVR trackers. The sensing and fusion category remains IMU-based SlimeVR tracking, so calibration, drift management and body-proportion setup still matter.
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A thinner tracker that moves less on a strap could improve practical consistency; that is a reasonable mounting inference, not a verified accuracy advantage. Treat comfort, battery life and accuracy as separate buying criteria rather than assuming one guarantees the others.
How many trackers do you need?
SlimeVR’s general documentation says at least five trackers are required for proper full-body tracking, while Butterfly bundles start at six because they package specific layouts.
| Bundle | Placement and use | Important limitation |
|---|---|---|
| Six-tracker Core Set | Hip, knees and chest; feet contribute position | Feet do not provide rotational tracking |
| Eight-tracker Enhanced Core Set | Hips, knees, chest and feet | Adds foot orientation |
| Ten-tracker Full-Body Set | Hips, knees, chest, feet and elbows | More expressive upper-body movement |
| Seventeen-tracker Motion Capture Set | Expanded upper-body and head coverage | Designed for broader mocap capture |
The bundle descriptions are on the Crowd Supply product page. A single tracker is an expansion or experiment, not a complete full-body system, and it still needs a compatible dongle.
Compatibility: PC, standalone headsets and Android
The dongle can connect to a PC, supported standalone headset or Android phone. Some bundles include a USB‑A-to‑USB‑C adapter; a device without USB‑A may require an OTG adapter. Standalone VRChat use still depends on USB host support, SlimeVR Server support on the host and the application’s OSC/network configuration. Compatibility is not universal for every phone or headset, so check current software requirements before ordering.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Repair Windows errors before they cause bigger problems3Fix the driver behind crashes, sound loss and screen glitchesOn PC, Butterfly is intended for SlimeVR-supported applications such as SteamVR and VRChat. SlimeVR’s open hardware and software ecosystem also enables community integrations, but software and firmware versions matter.
Setup and calibration
- Install the current SlimeVR Server on the chosen host.
- Plug in the Butterfly receiver dongle.
- Power on the trackers and wait for the server to detect them.
- Assign each device to its body location.
- Run automatic mounting calibration.
- Set or measure body proportions, including torso and leg dimensions.
- Launch SteamVR, VRChat or another supported application.
- Repeat mounting calibration whenever a tracker’s orientation or physical position changes.
- Use a yaw reset or full reset when drift or alignment errors appear.
Menu labels can change as SlimeVR evolves. The Smol documentation warns that newer devices may be incompatible with older server versions and may require frequent firmware updates.
Common problems and fixes
Trackers are not detected
- Confirm the dongle is connected and SlimeVR Server is running.
- Power-cycle the trackers and check that they have charge.
- Update SlimeVR Server and tracker firmware if the hardware is new or missing.
Only some trackers appear
- Move the host and receiver closer to the trackers.
- Check that the receiver is not obstructed by a PC chassis or other radio-blocking object.
- Verify that the setup does not exceed the dongle’s stated maximum of ten Butterfly trackers.
Legs or feet point backward
Check each body assignment, then repeat automatic mounting calibration. A tracker mounted at a new angle needs recalibration.
The avatar’s proportions look wrong
Repeat body-proportion calibration and manually correct torso or leg-length values when necessary.
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Tracking drifts
Perform a yaw or full reset. If a tracker physically shifted, remount it and calibrate again.
Standalone use fails
Check USB host or OTG support and the OSC/network path between the standalone device and SlimeVR software.
These procedures follow SlimeVR guidance; receiver placement advice is practical troubleshooting rather than a Butterfly-specific laboratory result.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Bundles, prices and availability
The following prices and shipping date were displayed on Crowd Supply on August 18, 2026 and can change. Current orders listed October 30, 2026 shipping.
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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware match| Product | Contents | Price |
|---|---|---|
| Core Set | Six trackers and dongle kit | $279 |
| Enhanced Core Set | Eight trackers and dongle kit | $364 |
| Full-Body Set | Ten trackers and dongle kit | $449 |
| Full-Body Sakura Special Edition | Ten pink trackers, dock and accessories | $499 |
| Motion Capture Set | Seventeen trackers, two dongles, straps and patches | $788 |
| Feet or elbows upgrade | Two trackers | $85 |
| Head upgrade | One tracker | $45 |
| Single tracker | Tracker only | $40 |
| Dongle kit | Receiver and adapters; up to ten trackers | $19 |
| Charging dock | Charges up to ten trackers; AC adapter excluded | $49 |
| Iron-on patches (20) | Loop material for clothing | $20 |
| Belt clips (two) | Belt mounting hardware | $10 |
US shipping was listed at $8 and worldwide shipping at $18 for the main Butterfly products. The normal Core, Enhanced Core and Full-Body bundles do not automatically include the optional charging dock.
Which Butterfly bundle makes sense?
- Choose Core if the lowest-cost prebuilt entry matters and foot rotation is not essential.
- Choose Enhanced Core for the broadest VRChat fit: it adds foot rotation without the ten-tracker price.
- Choose Full-Body if elbow tracking is important for expressive avatars.
- Choose Motion Capture when you need expanded upper-body and head coverage rather than ordinary social-VR tracking.
- Buy individual trackers or upgrades only when you already have a compatible receiver and a clear expansion plan.
Butterfly versus older Wi‑Fi SlimeVR trackers
| Category | Older official Wi‑Fi tracker | Butterfly / Smol approach |
|---|---|---|
| Wireless link | 2.4 GHz Wi‑Fi | Custom 2.4 GHz ESB |
| Receiver | No dedicated tracker dongle | Dedicated dongle required |
| Typical weight | About 50 g in SlimeVR’s comparison | About 10–15 g for Smol; Butterfly claims under 10 g |
| Battery comparison | About 18–20 hours | About 40–60 hours for Smol; Butterfly claims up to 48 hours |
| Range | Wi‑Fi coverage | About 7–12 m for general Smol guidance; Butterfly claims over 10 m |
| Setup | Wi‑Fi credentials and network dependency | Plug in dongle; no tracker router configuration |
| Primary strength | Range and established workflow | Low weight, comfort and battery life |
All figures in this comparison come from SlimeVR’s documentation or product page, not independent testing.
Alternatives
DIY Smol trackers
The Smol Slime documentation and SlimeVR GitHub organization support builders who want custom boards, cases or lower component costs. DIY requires assembly, firmware flashing and potential self-repair; component prices vary, so there is no reliable fixed total.
Sony mocopi
Sony mocopi is a separate commercial sensor ecosystem with a documented, but beta, SlimeVR integration. Its workflow uses the mocopi phone app, SteamVR, SlimeVR, Wi‑Fi, body-proportion calibration and mounting calibration. It suits buyers who prefer Sony hardware over open Butterfly hardware.
Shiftall HaritoraX
Supported HaritoraX models can connect through the SlimeTora bridge. The documented setup may involve HaritoraConfigurator, SlimeTora, SlimeVR Server and COM-port configuration, making it most attractive to users already invested in that ecosystem.
Who should buy Butterfly?
Butterfly is a strong fit for users who find conventional trackers uncomfortable, spend long sessions sitting or lying down, dislike configuring Wi‑Fi devices, or want long battery life in a small open-software system. It is a weaker fit for people who need immediate delivery, very long range, a dongle-free setup, extensive independent testing or optical-style positional tracking.
Verdict: Butterfly is a substantial ergonomics and battery refinement of SlimeVR’s IMU approach—not an optical-tracking replacement and not an automatic accuracy revolution. The Enhanced Core Set is the most balanced choice for many VRChat users, provided they accept the dedicated receiver, calibration work, shorter-than-Wi‑Fi range and October 30, 2026 listed fulfillment date.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
