Most dual driver iems are, typically, configured to have one balanced armature (BA) driver for the higher frequencies and a single coil dynamic driver for the lower frequencies. The Hidizs Mermaid MS2 iem uses this same dual driver configuration (using a Knowles RAD 33518 BA driver) but, instead of single coil dynamic driver, the 10.2mm dynamic driver inside the Hidizs MS2 uses two voice coils and two diaphragms, which effectively makes the Hidizs MS2 function like a triple driver iem!
The Hidizs MS2 dual coil dynamic driver splits the bass and midrange frequencies between the two coils, resulting in clear vocals and lively, well defined deep tones, which you can easily recognize when listening to electronic music that has beats, piano, vocals or drums in it. 
The Hidizs MS2 do a good job at letting you hear the lower bass frequencies (sub-bass and mid-bass), which you typically can't when the bass is boomy/ overemphasized. Complimenting the energetic bass, it's also clean and detailed treble. The Knowles BA driver produces good instrument separation too, thanks to the wide soundstage created, which is one of the advantages you get with multi driver iems.

The MS2 iem earphones deliver superb audio dynamics, thanks to high sensitivity (112dB) and low impedance (18 Ohm). Since the MS2 iems are high sensitivity and low impedance, they use high current and low voltage; hence they can be easily driven from a smartphone. That said, having a headphone dac/amp such as the S3 Pro or the DH80S dac/amp combo also helps for getting the best performance out of them.
Being iem earphones, the Hidizs MS2 also come with a detachable cable, which is a litz braided cable with a transparent sheath that exposes the wiring - two silver plated wires and two oxygen-free copper (OFC) wires. Like most litz cables, the strands are twisted to make the cable more flexible and also help with interference, which is the same reason Ethernet cables use twisted pair cables. The MS2 litz cable terminates in a 3.5mm connector with straight metal plug and gold plated pin connectors (2-pin 0.78mm), which are housed inside small rubber plugs. The 2 pin connectors sit flush against the plugs without being recessed or extruded like other 2 pin iem cables.
The MS2 litz cable pin connectors have blue/red dot indicators to differentiate the left channel (blue) and right channel (red). Some iem 2-pin connectors also have smaller blue dots to indicate the polarity orientation of the pins to prevent a mismatch, which would cause the sound to be out of phase. The 2 pin connectors on the MS2 litz cable don't have these smaller blue dots so, you simply have to make sure the pin plugs face the same direction. There is no user guide included that illustrates this but, this is how detachable iem earphones work 
The 3.5mm metal plug integrates two copper rings and, it's reinforced with a transparent strain relief. More copper accents can be found on the cable cinch and y-splitter, which has an interesting bullet shell casing design.
Hidizs branding can be seen etched throughout the MS2 iems, as well as Hidizs.com etched on the sides. Having the website address displayed so prominently looks a bit out of place and doesn't compliment the design aesthetics. Despite being called MS2, they are newer than the MS4 iems, which launched in 2019. The MS2 iem earphones are dual drivers while the MS4 are quad driver iem earphones with an aluminium body shell.

The MS2 have a transparent resin body shell that exposes the internal electronics, while the faceplate has iridescent-like confetti embedded in it, which changes color when light shines into it. While the Hidizs MS2 shell is made of resin, the nozzle necks are metal gold plated and capped with metal mesh tips.
The MS2 earphones weigh 5 grams each, while the cable weighs 17 grams and measures 1.2 meters long. The total weight is 27 grams, which is naturally lighter than the MS4 iems (weigh 36 grams). The Hidizs MS2 iem earphones come nicely packaged inside a hard box and a protective foam insert with two small preformed cutouts for the earpieces.

Accessories include a square-shaped storage box/carry case that weighs 108 grams and measures 8cm long, 8cm wide and 4cm high. The storage box has a similar construction to a jewelry box with soft rubber material lining the inside. The lid is hinged so, it stays upright when opened, although it is not a friction hinge with resistance; hence the lid cannot be kept ajar. The storage box has a magnetic closure, which is strong enough to prevent the lid from opening accidentally.
The internal depth of the storage box is 3cm high, which is just about enough space for storing the earphones, cable and tip holders.The storage box has Hidizs branding and a brushed finish on top and glossy finish throughout. The eartip plastic holders have bowl shaped, silicone ear tips of different sizes with wide bore and narrow bore. You can buy the Hidizs Mermaid MS2 from Hidizs. Check out the review of the Hidizs AP80 mp3 player.