Short answer: a tie on sound quality. Both are rated 3.9/5 (#297 and #312 of 450 in-ear headphones) at nearly the same price ($20.89 vs $23), so choose on features and fit.
Buy the KZ Castor or the Sony WI-C100 on features: they are rated the same for sound quality at close to the same price.
Still deciding? The full Headphones rankings cover every ranked option.
Specifications Side By Side
| KZ Castor | Sony WI-C100 | |
|---|---|---|
| Price | $20.89 | $23.00 |
| Ranked | #297 of 450 in In-Ear Headphones | #312 of 450 in In-Ear Headphones |
| Form Factor | In-ear | In-ear |
| Back | Closed | Closed |
| Harman Preference Score | 73 (median of 11 squig.link measurements, calibrated to AutoEQ) | 72 (median of 3 squig.link measurements, calibrated to AutoEQ) |
| Deviation From Target | 2.01 dB standard deviation | 1.94 dB standard deviation |
| Tonal Tilt | -0.29 (negative is warmer, positive brighter) | -0.49 (negative is warmer, positive brighter) |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-0.0 dB at 30 Hz) | Within 6 dB of target down to 20 Hz (-2.2 dB at 30 Hz) |
| Connection | Wired | Wireless |
| Driver Type | Dynamic | Dynamic |
| Drivers | 2 x dynamic | 1 x 9mm dynamic |
| Sensitivity | 105 dB | - |
| Frequency Response | 20Hz - 40kHz (Manufacturer specified) | 20Hz - 20kHz (Manufacturer specified) |
| Weight | - | 0 lbs (20 g) |
| Active Noise Cancelling | - | No |
| Battery Life | - | 25 hours (Manufacturer specified) |
| Bluetooth Version | - | 5.0 |
| Bluetooth Codecs | - | SBC, AAC |
| Built-in Microphone | - | Yes |
| IP Rating | - | IPX4 |
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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
KZ Castor: $20.89 Amazon eBay
Full KZ Castor review and specifications →
| Back | Closed |
|---|---|
| Connection | Wired |
| Deviation From Target | 2.01 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 2 x dynamic |
| Form Factor | In-ear |
| Frequency Response | 20Hz - 40kHz (Manufacturer specified) |
| Harman Preference Score | 73 (median of 11 squig.link measurements, calibrated to AutoEQ) |
| Sensitivity | 105 dB |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-0.0 dB at 30 Hz) |
| Tonal Tilt | -0.29 (negative is warmer, positive brighter) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
Sony WI-C100: $23.00 Wireless Amazon eBay
Full Sony WI-C100 review and specifications →
| Active Noise Cancelling | No |
|---|---|
| Back | Closed |
| Battery Life | 25 hours (Manufacturer specified) |
| Bluetooth Codecs | SBC, AAC |
| Bluetooth Version | 5.0 |
| Built-in Microphone | Yes |
| Connection | Wireless |
| Deviation From Target | 1.94 dB standard deviation |
| Driver Type | Dynamic |
| Drivers | 1 x 9mm dynamic |
| Form Factor | In-ear |
| Frequency Response | 20Hz - 20kHz (Manufacturer specified) |
| Harman Preference Score | 72 (median of 3 squig.link measurements, calibrated to AutoEQ) |
| IP Rating | IPX4 |
| Sub-bass Extension | Within 6 dB of target down to 20 Hz (-2.2 dB at 30 Hz) |
| Tonal Tilt | -0.49 (negative is warmer, positive brighter) |
| Weight | 0 lbs (20 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons