Most earbuds these days are made by injecting melted plastic into a mold via an injection molding machine, or by extruding heated thermoplastic filament via an FDM (Fused Deposition Modeling) printer to make the earbud shell.
The Brainwavz Koel earphones however, are made using a 3D resin printer which is the same type of printer used to print high quality Dungeons & Dragons (D & D) miniature and Role-Playing-Games (RPG) miniature figures.
Instead of letting the plastic to cool naturally like with injection molding and FDM printing, resin 3D printing use a bright UV light that hardens the cast layer by layer. This process works a bit like the Bondic UV light pen.
Compared to filament-based printing, 3D resin printing is definitely more versatile and it produces clear, detailed casts like can be seen with the Koel translucent shell housing. You can even see the balanced armature component inside the Koel earphones which is pretty neat.
Another neat feature that makes the Brainwavz Koel earphones stand out from most other earphones is the y-MMCX cable which can be removed. The Koel MMCX cable is detachable from the earphone shells and can be replaced should it wear out or break.
You can buy any third party earphone replacement cable with MMCX connectors, although Brainwavz sells their own earphone replacement cable with MMCX connectors.
Do keep in mind though that the Brainwavz Koel are unbalanced earphones with a 3.5mm jack. You can tell they are unbalanced because of the two black rings (TRS) on the plug (balanced earphones have three black rings). The plug connector itself is gold-plated which is nice.
A useful cinch slider is found along the Y-cable junction which turns the Koel earphone cable into a cinch cord that functions just like the hem cinch cord of a jacket. Moving the cinch slider up closes up the Y-cable for a snug fit around the neck which is nice for a more secure fit.
Speaking of fit, the Brainwavz Koel earphones are designed to be worn around the ears with the cable running along the back of the ears which actually happens to be the best way to wear earphones because running the cable behind the ear lobes (as opposed to straight down) eliminates cable noise (microphonics).
The actual rubber section of cable that goes around the ears has properties similar to memory foam so it softens with your body heat and regains its original shape quickly.
As far as sound, the Koel earphones have a neutral (flat) sound signature without the "sound effects" you get with dynamic drivers which make the highs and low frequencies more lively. With that said, balanced armature drivers have one major advantage and that is accurate sound reproduction.
The Koel earphones do a good job at clear instrument separation with a wide sound stage thanks to their larger than average size earbud shells, much larger than similar spec earbuds such as the S0 earphones, Delta IEMs or Blu-100 earbuds.
Accessories-wise, the Koel earphones come with a fabric zip up hard-shell case where you can store the earphones and the other included accessories like the shirt clip and silicone tips of different sizes to fit different size ear canals.
Talking about eartips, they are a very underrated part of earphones. Wearing the wrong size eartip can make a good sounding pair of earphones sound not as good so it's nice that Brainwavz also includes a pair of foam tips along with the silicone tips since foam eartips do a better job at isolating noise because they seal the ear canal completely, which means better bass response.
Brainwavz includes a pair of Comply foam T-100 tips which are some of the best foam tips you can buy but it's worth knowing that Comply foam tips come with different bore hole (core) sizes to fit  specific nozzles of earphones.
The T-100 tips for instance have a 3mm core size while the T-500 tips have a 4.5 mm core size. If in doubt, it's worth checking out the Comply Compatibility chart.