Shure SE535-CL

If you never used in-ear, which I had not until I got these, you should realy try it out.
I will never go back to a monitor.
I use these mainly with an e-drum kit and find it works great.
One big reason for trying in-ear to start with, is that in one band I play all songs to a click track and have to use headphones. They just don´t look alright on stage and a lot don´t cancel noise well enough. You will not have any problems with that with these. Like regular industrial ear plugs these make you not hear what other people are saying but you also talk VERY LOAD :)
The sound is great, for being a small unit. Of course bass is not gonna be at par with a nice set of headphones but there´s definitly enough for a pleasant sound.
I can turn down the volume a lot because the noice cancellation is so good. So not as much ringing in my ears at the end of the gig, which to me is one of the biggest advantages with in-ear.
I was worried that I would have a hard time getting a proper fit, and at the first and second gig I was struggling a bit. But after a few tries they sit perfect and don´t move at all. There´s a lot of different "ear pieces" in both rubber, foam and plastic and many sizes.
So all in all this is one of favorite piece of kit.

I use these IEMs with my live band, both in a super-noisy rock settings as well as a less-noisy function band settings and they're great. I bought the 535's after my knockoff Chinese 6-driver IEMs died a little over a year down the road. These 3-driver monitors sound just as clear and loud and I know that I have a warranty for these and I will be able to repair them with confidence.
I took a star off for noise cancelling as this is of course not as perfect, as it would be with molded earpieces and another star off due to my ears actually getting a little tired of the earphones.

This is my third pair of SE535s. They come supplied with a decent range of ear buds to ensure a good fit, give great sound isolation (can almost be too much at times), and have great sound quality. With the right ear bud choice they are comfortable to wear for long periods of time. So why four stars? The cables are notorious for breaking -- an easy fix but temporarily renders the item useless. I've had great support from Shure/Thomann with regard to this issue, but it does take time to get the item sent off, evaluated, and replaced. If you don't have a spare set of in-ears for gigs I'd suggest buying a spare cable in case the cable gives up on the job. Overall, I think you'd struggle to get something better in this price range but be aware of the cable issue.

Good earphones in overall.
If you had experience with something like Westone's
IEMs, you might find Shure's are a little uncomfortable (just not so ergonomic, but if you do not use them 24/7 they are bearable, and later you will get use to them any way), But Westone's are not so reliable.
Shure's are much better.

Sound is good as well, however not very linear.
Sensitive highs, powerful and clear lows. Many people notice, that mids are a little too loud. You must use EQ for music listening.
They can be good for voice monitoring, I think, but this is just my supposition.
However they provide better sound isolation, than Westone's, and they sits better
in the ear channels, even when you use the same ear tips (yes - Westone's and
Shure's SEx35 can be used with the same SHURE PA 910 ear tips)

I must notice, that, if you use them 24/7, then the moist from your ears will start
to accumulate inside the earphones, then there will be a drops of water, and the water
can cause some cooper surfaces to corrode, thus causing damage to the circuits and
cable's sockets from inside - this is not fixable, and cleaning the sockets will not help. NEVER use them 24/7. However, that is not very pleasant anyway, because your year channels will start to itch after like 8 hours of usage )).

In overall - very good quality and performance/price rate.
The only better IEMs are probably 4-drivers Shure IEMs (it is quite a new model), and custom Ultimate Eears IEMs, but their prices are beyond my
pocket size )).

First impression: if you put them on, you will never want to take them off :).