The hex keys work quite well. Good length & rigidity. Fit precisely into the bolts. Rounded keys work well for recessed bolts like those on my disc brakes.
The holder works. Good value & feel built to last.
The hex keys are long enough to generate enough torque. The heads are precise to the size. There is a 8mm adapter to convert 6mm to 8mm, so you're definitely saving some weight. The bigger keys have a ball-end so you can reach some screw heads at angles where the straight key won't be able to reach. The rubber holder grips the keys in place. And Icetoolz can be trusted hard. Must check it out.