I bought these mud guards since for such a cheap price they had quite positive reviews. However being a slight bike novice (but not wanting to get a muddy back on my way to work) I had not realised that where the mud guards attach to the A shaped bit above the wheels is where I have reflectors attached on small mounting brakets. However my dad was able to remove them and we found the guards still fitted with the refelectors reattached ontop. I was at first worried they wouldn't fit because of my bikes v-brakes being in the way but having attached them, and rode back and forth to work, they've been fine and I have not got mud splattered up my back/bag.
The circular clip on to back guard, which is supposed to clip onto the seat post for extra sturdiness, didn't fit onto mine as the mud guard was too short to reach that far. so it touches the post but is not attached. Seems to be okay just attached above the wheel though. (I've fallen off my bike since and they stayed on - just not me - ouch!)
The plastic is okay, I'm sure you could probably get better ones, but for the price they don't look too bad and do the job which is the most important thing.
Just make sure you know you know your wheel size (24-26in) to make sure they fit - check the inner metal rim on yer bike :)