i ordered bulk pack of brandless, and some areas once its applied do not want to stay down. there is nothing under like hair or dust but for whatever reason the adhesive layer seems to have random parts where its not strong enough.. thats pretty cheap tho so try it.
i just recieved 5 for the back of the phone for $3 The back fits perfectly but you get a air crease along where the aluminum meets the glass...but overall not that noticeable and it stays on flat even if you have a bumper case. The wet install ones always peel off at the edges.
I bought cheap SP's (5 for $1.99) on eBay and they are great. They aren't the same as yours. I usally go through 3 of them until I have it on perfect, but I was able to get one on perfectly the first time. It looks and feels great.