Quality varies - I had a pair that needed a lot of balancing, then the next pair was almost flyable as is. Holes may need reaming for mounting in the blade grips, but this takes 10 seconds with a hobby knife.
Bottom line: If you have a TREX 450, you should have a couple pairs of these on the shelf. They come in handy if you're practicing a new maneuver and don't want to ruin your $30 a pair carbon blades.
These blades are great. For the price you can't get any better. I added a little weight for better balance, but would have work great right out of the package. Four stars on the quality for blade balance. Will buy more. (Posted on 10/7/2013)