How We Research
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
If you want a metal-built, five-driver monitor with a microphone for calls and gaming chat, choose erjigo KZ ZS10; if you need a bass-forward IEM you can physically re-tune with a switch, choose YINYOO KZ Castor.
• erjigo KZ ZS10 — biggest strength: A 4BA+1DD five-driver hybrid per side with a very wide 7Hz–40,000Hz range, 111dB sensitivity and a built-in HD mic. That's a lot of hardware and hands-free convenience in one wired package.
• erjigo KZ ZS10 — biggest trade-off: It's a fixed tuning. There's no switch, no app, no way to nudge the sound later — you either like the house signature or you don't. The 24-ohm load also rewards a decent source.
• YINYOO KZ Castor — biggest strength: A 16-ohm, 103dB dual-dynamic design with a 4-level adjusting switch. KZ claims that switch creates up to 16 different audio profiles, so you can shift the low end to taste.
• YINYOO KZ Castor — biggest trade-off: The version in this data sheet ships without a microphone, so it's a listening-first set, not a headset. It's also the less sensitive of the two on paper.
• Who each pick is for: The ZS10 is for the person who wants one wired IEM to do music, video meetings and game chat. The Castor is for the listener who wants to chase bass and experiment with tuning.
The ZS10 Pro is the more "everything" pair of the two. Per side you get four custom balanced armatures (2×30095 for highs, 2×50060 for mids) plus a 10mm dual-magnetic dynamic driver, which is where I'd expect the punch and body to come from. The claimed frequency range runs 7Hz to 40,000Hz, and sensitivity is rated at 111dB/mW. That combination — a lot of drivers plus high sensitivity — suggests an energetic, detail-forward presentation with strong upper-end clarity. In my opinion, that's exactly the profile that suits monitoring, critical listening and gaming, where you want to pick out footsteps and small cues without cranking the volume.
Build is where it separates from cheap plastic IEMs. The faceplate is 304 stainless steel with a sand-black finish, and the cavity uses imported resin. That metal-resin pairing should feel substantial and hold up to daily bag life better than an all-plastic shell. The cavity is shaped from cochlea data for a secure fit, and KZ rates the passive isolation at up to 26dB — enough to take the edge off a bus, a train or a noisy office. The cable is detachable via a gold-plated 0.75mm 2-pin connector with a limit-slot design meant to stop pin breakage, and because it detaches you can swap it later or move to a Bluetooth module. It terminates in a 3.5mm jack, and the cable runs roughly 4.1 feet. The mic is the practical bonus: one-key control for answering calls, ending them, or skipping tracks. You get three pairs of tips (S/M/L) and a manual in the box, and it's sold in purple, black or blue.
Who should buy it: anyone who wants a single wired IEM to cover music, video calls, online meetings and game chat, and who values a metal build and a replaceable cable. Who should skip it: tinkerers who want to change the tuning themselves, and buyers who want maximum bass flex — the ZS10 gives you one signature, and you live with it.
The Castor is built around a different idea: give the listener control. It uses a stacked dual-dynamic setup — a 10mm dual-magnetic dynamic driver — rather than a mix of driver types. Impedance is 16 ohms and sensitivity is 103dB, with a 20Hz–40,000Hz range. Lower impedance means it's easy to drive from a phone or a cheap dongle, though the lower sensitivity means it will want a bit more volume than the ZS10 to hit the same loudness. The tuning target is the Harman FR curve, and this particular version is the "Harman Target with Improved Bass" edition — KZ says it boosts low-frequency sensitivity and dynamics while keeping mids and highs aligned to that curve. Translation: expect a warm, bass-led sound rather than a flat studio one.
The headline feature is the 4-level adjusting switch. Flipping it changes the low-end response, and KZ describes the combinations as up to 16 different audio profiles. In practice, that means you can make it thunderous for hip-hop and electronic, then dial it back for podcasts or acoustic tracks without buying a second pair. That's genuinely useful if your taste is broad. The shell mixes metal and plastic, and the eartips are silicone with an ergonomic shape, supplied in three sizes for different ear canals. KZ also makes a point about the molding process — an integrated injection molding method with tolerances around 0.01mm versus roughly 0.1mm for typical 3D printing — which speaks to consistency of the internal structure rather than anything you'd see. Isolation is passive, via the tip seal, and the connection is a standard 3.5mm wired jack. The version in this data sheet ships without a mic.
Who should buy it: bass lovers, and anyone who enjoys fiddling with tuning to match a track or a mood. Who should skip it: people who take a lot of calls or game chat and need a built-in microphone, and anyone who wants a set-and-forget signature.
Side-by-Side: Which Should You Choose?
• Best for calls, meetings and game chat → erjigo KZ ZS10. It has the built-in HD mic with one-key media control; the Castor in this data sheet has no mic.
• Best for tuning flexibility → YINYOO KZ Castor. The 4-level switch lets you reshape the sound; the ZS10's tuning is fixed.
• Best for detail and upper-frequency clarity → erjigo KZ ZS10. Four balanced armatures plus a dynamic driver, rated to 40,000Hz, with 111dB sensitivity — in my opinion the more analytical of the two.
• Best for easy driving from a phone → YINYOO KZ Castor. At 16 ohms it's the lighter electrical load, even though the ZS10 is more sensitive.
• Best for build feel and long-term durability → erjigo KZ ZS10. 304 stainless steel faceplate, resin cavity, and a detachable 0.75mm 2-pin cable designed to resist pin breakage.
• Best for isolation on a commute → erjigo KZ ZS10. KZ rates its passive isolation at up to 26dB; the Castor relies on its silicone tip seal without a published figure.
• Best for a fuss-free single-signature setup → erjigo KZ ZS10. Plug in, done. The Castor asks you to tune it.
I'd buy the erjigo KZ ZS10. The five-driver hybrid, the 304 stainless steel faceplate, the detachable 2-pin cable and the built-in mic make it the more complete wired IEM for everyday life — music, calls, meetings and gaming in one pair. The Castor is the more fun, more flexible listen, and if bass and tunability matter more to you than a microphone, it's the smarter pick. But for most buyers who want one do-everything set, I'd take the ZS10. Check the current price on Amazon before you commit, since both are budget-tier IEMs where value swings with whatever deal is live.
Not universally. The ZS10 wins on driver count, metal build, sensitivity and the built-in mic. The Castor wins on bass tuning and the adjustable switch. Which is "better" depends on whether you want a headset or a tunable bass monitor.
Does the KZ Castor have a microphone?
The version covered here — the Harman Bass edition, "without mic" — does not. If you need hands-free calls, the ZS10 includes an HD mic with one-key control.
On paper, the Castor. It's the improved-bass Harman edition with a 4-level switch for extra low-end shaping. The ZS10 is more of an articulate, detail-forward monitor with a 10mm dynamic driver handling the lows.
Yes. It uses a detachable gold-plated 0.75mm 2-pin cable with limit-slot protection, so you can swap cables or move to a Bluetooth module later. The Castor's data sheet doesn't list a detachable cable.
The Castor, at 16 ohms versus 24 ohms for the ZS10. But the ZS10 is rated higher for sensitivity (111dB vs 103dB), so it needs less volume for the same loudness. Both use a standard 3.5mm wired jack.
As an Amazon Associate I earn from qualifying purchases.
We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.
When you buy through links on this page, we may earn a commission from qualifying purchases at no extra cost to you.
Amazon and the Amazon logo are trademarks of Amazon or its affiliates. This site is an independent third-party review and is not affiliated with, endorsed by, or sponsored by Amazon or the product brands mentioned.