The one store-bought divider I got a few years ago I found was very flimsy and clear so my fish could see each other very easily. I attempted to put plants in front of it on both sides, but the fish just swam around them. Really, I wouldn't recommend dropping the cash on a store-bought divider. Homemade ones are cheaper, sturdier, and much MUCH less see-through.
I make all of my dividers using this method: http://www.tropicalfishkeeping.com/d...ividers-21866/
...but with a bit of my own twist. I've discovered that if you use two sheets of the craft mesh and double-up on it, then trim a row or two until the divider fits snugly on the sides without bending its more stable, even less see-through, and a little more aesthetically pleasing as well.
With the doubled-up craft mesh, i have noticed VERY little flaring, just a bit upon introduction with a few of my more feisty fish, and my mellower/shyer ones didn't even bother at all.....so I assume they really can't fully see one another, only a shadow.
I've had fantastic success with no stress and only one mishap(my PK jumped over, but that was easily fixed by an extra piece of mesh stuck between the two pieces in the divider to make it higher in that small area) with this divider method.