Short answer: a tie on sound quality. Both are rated 4.3/5 (#133 and #127 of 450 in-ear headphones) at nearly the same price ($99.99 vs $99.99), so choose on features and fit.
Buy the Fosi Audio IM4 or the Moondrop Kato on features: they are rated the same for sound quality at close to the same price.
Want more options? Browse the full Headphones rankings.
Specifications Side By Side
| Fosi Audio IM4 | Moondrop Kato | |
|---|---|---|
| Price | $99.99 | $99.99 |
| Ranked | #133 of 450 in In-Ear Headphones | #127 of 450 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 78 (median of 5 squig.link measurements, calibrated to AutoEQ) | 78 (median of 34 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 1.75 dB standard deviation | 1.70 dB standard deviation |
| Tonal Tilt | -0.02 (negative is warmer, positive brighter) | -0.14 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-1.4 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (-2.2 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Dynamic | Dynamic |
| Drivers | 1 x 10mm dynamic | 1 x 10mm dynamic |
| Impedance | 21 ohms | 32 ohms |
| Sensitivity | 109 dB | 123 dB/Vrms |
| Weight | 0 lbs (7 g) per earbud | - |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) | 10Hz - 45kHz (Manufacturer specified) |
| Built-in Microphone | No | No |
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Prices on this page were last checked October 11, 2026 at 4:59 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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The Two Headphones In Full
Fosi Audio IM4: $99.99 Amazon eBay
Full Fosi Audio IM4 review and specifications →
| Released | 2025 (1 year ago) |
|---|---|
| Back | Closed |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 1.75 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 1 x 10mm dynamic |
| Form Factor | In-ear |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) |
| Harman Preference Score | 78 (median of 5 squig.link measurements, calibrated to AutoEQ) |
| Impedance | 21 ohms |
| Sensitivity | 109 dB |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-1.4 dB at 30 Hz) |
| Tonal Tilt | -0.02 (negative is warmer, positive brighter) |
| Weight | 0 lbs (7 g) per earbud |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
Moondrop Kato: $99.99 Amazon eBay
Full Moondrop Kato review and specifications →
| Released | Sep 2021 (5 years ago) |
|---|---|
| Back | Closed |
| Built-in Microphone | No |
| Connection | Wired |
| Deviation From Target | 1.70 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 1 x 10mm dynamic |
| Form Factor | In-ear |
| Frequency Response | 10Hz - 45kHz (Manufacturer specified) |
| Harman Preference Score | 78 (median of 34 squig.link measurements, calibrated to AutoEQ) |
| Impedance | 32 ohms |
| Sensitivity | 123 dB/Vrms |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-2.2 dB at 30 Hz) |
| Tonal Tilt | -0.14 (negative is warmer, positive brighter) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons