This is a very simple prop balancer which is easy to use. Fit the prop hub in between the two tapered cones, then hold the two pointed ends of the shaft lightly between thumb and forefinger, let the prop settle and you should quite easily see which blade is the heavier.
1 spin of 2 is bad quality, the shaft twisted and the extremity are flat no conical.
After some work on it, that become correctly for the shaft, but for the Spin I replacing it with a nut and washer.
I hope Hobbyking have to check the item in stock because my DIY balancer with threaded rod is better if no work is done in this part.
That cost the little price maybe...