Short answer: a tie on sound quality. Both are rated 3.9/5 (#482 and #533 of 1291 in-ear headphones) at nearly the same price ($20.89 vs $22.80), so choose on features and fit.
Why pick the KZ Castor: The median of 11 hobbyist measurements gives it a solid Harman preference score of 73 with a 2.01 dB spread, and its mids sit within about 1 dB of target, so vocals and instruments sound natural. The catch: A 5.1 dB peak near 11.9 kHz can make cymbals and sibilance sound sharp.
The case for the TANGZU Wan’er S.G II: A very cheap single dynamic IEM, the second generation of the TANGZU Wan’er S.G. Watch for: Treble sits about 4.0 dB below target, a dark, relaxed balance.
Buy the KZ Castor or the TANGZU Wan’er S.G II 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.
The median of 11 hobbyist measurements gives it a solid Harman preference score of 73 with a 2.01 dB spread, and its mids sit within about 1 dB of target, so vocals and instruments sound natural.
Amazon $20.89 eBay
A very cheap single dynamic IEM, the second generation of the TANGZU Wan’er S.G.
Amazon $22.80 eBayPrices on this page were last checked October 16, 2026 at 5:46 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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Specifications Side By Side
| KZ Castor | TANGZU Wan’er S.G II | |
|---|---|---|
| Price | $20.89 | $22.80 |
| Ranked | #482 of 1291 in In-Ear Headphones | #533 of 1291 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 | 2.07 dB standard deviation |
| Tonal Tilt | -0.29 (negative is warmer, positive brighter) | -0.41 (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 (-1.3 dB at 30 Hz) |
| Connection | Wired | Wired |
| Driver Type | Dynamic | Dynamic |
| Drivers | 2 x dynamic | 1 x 10mm dynamic |
| Sensitivity | 105 dB | 113.5 dB |
| Frequency Response | 20Hz - 40kHz (Manufacturer specified) | - |
| Impedance | - | 19 ohms |
Frequency Response Compared
Both headphones’ measurements overlaid on the Harman target. Above the target sounds louder in that range, below it quieter. Each curve is the median of several independent measurements, shifted so its 500 Hz to 2 kHz average sits at 0 dB, so only the tuning is compared.
Measurement data: the KZ Castor from bassyalexander, flare, gadgetrytech, harpo, hbb, hobbytalk, melatonin, musicafe, practiphile, pw and superreview; the TANGZU Wan’er S.G II from lestat, pw and sl0the, all via squig.link.
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