These are definitely a budget in ear monitor in both price and performance. I wasn't expecting a lot from them, but other t.bone gear delivers really well so I was hopeful they'd be usable in an emergency.
As a bass player, these weren't great for me at all as I just couldn't get a good seal in my ear canal which is essential to maintain the bottom end. The silicon tips weren't a good fit and even when in place, don't provide much in the way of isolation or noise-cancelling.
Our singer has used them once or twice and they're okay if all you need is to hear your voice a bit more clearly and at a slightly lower volume.
If you're a singer on a tight budget then these could work for you, but I would recommend spending as much of your IEM budget as you can on quality phones as the difference between these budget ones and, for example, Shure SCL-3, is vast.