The "gimmik" is actually quite robust and I would agree with the previous comments. There are,
however, a few things to bear in mind, well certainly in my personal opinion. As is not unusual for
most products from Asia, the wrist strap is very tight and may have to be altered for those who have
thick wrists otherwise there could be a few issues with blood circulation. The access to the
tutorial is over a QR code which brings you to a 26 minute video in S.Korean with English subtitles.
It takes a while getting through this because even for the speediest readers you'll have to go back
to catch what was flashed up for a micro second. The main limitation for me is that wherever this is
performed you have to wear very dark clothes, preferably black and definitely no chance with white
or bright coloured clothing, you also can't do this without long sleeves. This doesn't detract from
the illusion itself, but it's worth pointing out in case this might be beneficial to know. There is
no complicated learning curve and the concept is simple but clever. As with everything else,
practice in front of a mirror is the key element.