Pros: Layering, Sound-stage and true low distortion,brutal!
Cons: Most of the accessories, transport bag and the cable mainly.

Conclusion: Applying a Hacks:replacing the cable with one of the iems in the form of a hanger for the ear, they turn out to be very comfortable to listen at home, I would never use them outside or doing activities with a lot of movement.
Regarding the sound, if you have a dedicated amplifier and apply a good dose of equalization in the bass and treble, it will blow your mind with its incredible capacity.

I love them, because of the incredible immersion in music that I experience with them, they are one of my favorites in my collection.

First I have to say these headphones sound great but monoprice has to work on the cables after dealing with the cables supplied I new that I had to purchase a better set. Well that was a nightmare but that’s a whole other story.
I would think that for a company that is known for quality cables that they would supply a better set. But as I stated earlier these headphones sound great with better cables.

Best IEMs I've used to date, the stock cord they come with suck for them, but it's perfect for my modded KPH30i. I will say they were uncomfortable until i realized switching sides and looping them over my ears solved 90 percent of the comfort issues.

Nice soundstage and detail, poor design nozzle, stock cable is too heavy to hand accordingly in your ear, otherwise is very nice product, can not use more than 2-3h , big nozzle hurt my ear , but I love sound of it with nice rebate , I’m happy for quality/price
Just update cable memory hook and you’re good to use

the size of the nozzle is definitely too big as well as the tips
the earhooks are poorly made
and the sound is shouty

They're fine headphones - the planar magnetic driver does make it better than the typical similar priced iem you'd buy on amazon or something.

That said, I can't exactly recommend these when chinese brands like KZ and CCA exist, whose 12 and 16 driver headsets surpass the M300 in every single way for similar or just slightly higher prices.

When compared to general earbuds, the M300s definitely would be in the top 10% of all. That said, if you're making a value comparison between the M300s and some of the cheaper chinese IEMs, brands like KZ and CCA are just better in every way.

Also, the M300s are a pain to wear. The left side's volume changes significantly based on whether the wire is twisted - don't think it should be doing that. Quality control on these isn't great.

For $50 these are amazing. Probably the cheapest planars you can get. The sound signature does require sometime getting use to. The fit isn't the best but it fits me fine. Really wide soundstage.

I feel like these are a bit lackluster for 50$ (Ordinarily 100$). Don’t get me wrong, unboxing them and seeing them for the first time felt cool as heck, but I feel like too much time and effort was wasted on flashy showmanship for a middle of the road earbud. The connectors on the earbuds themselves don’t inspire much confidence. You’ve got about 1/16 of an inch of actual connector. The sound could best be described as a very cheap M1060 (which I guess it is). The same Monolith flavor carries over, but everything is lacking. On my review of the M1060 I bragged about how well they handled bass without clicking. These click. And scratch. And make plenty of other unpleasant noise when cranked. The treble is... bad. It sounds very artificial. The mids are alright. But just alright. Both the M1060s and these being planar, I was ready for the same planar oomph in an earbud. I was not impressed. Even with the help of the Fiio A5, these are still just not good. Overall verdict has gotta be a 4/10. Keep trying guys, I still love you!

I'm not sure who these were designed for, but I don't think they're made for human ears. The clips barely keep them on my ears, and even then it's very uncomfortable. The tips included are strangely sized and the texture is too smooth to keep the phones in your ears without the clips.

So essentially, unless you have the very strangely shaped ears these were evidently designed for, these are unusable. It's a shame, because they sound pretty good.

These are my first planars. These are incredibly clean, have an excellent soundstage and imaging. I have a full size set of ESS cans with the Heil AMT. These have an even more detailed high end. Low end is nice and tight...not boomy at all. Just as expected from a planar driver. I listen to all types of music, except hip-hop. Lots of jazz and blues. Some have issues with the weight and comfort. I don't have an issue with either. I'm extremely happy with these. Getting them on sale was a bonus as they are worth the full price. Hats off to MP. I have several Monolith products including a subwoofer. All are extremely high quality. I see an amp with my name on it ! Thank You MP !