These mantra bracelets are filled with copper leaf, this is the copper viriation off the goldleaf. They are closed with a mantra and blessed in the temple by the Asian monks. Copper is a purifying metal, that's why this copper variation is symbolising purification.
The copper leaf has been sprinkled into the flexible tube off the bracelet.
They are water resistant and the copper will age very nice in time, so the longer you'll where it the better is looks.
