These mantra bracelets are filled with copper leaf, this is the copper viriation off the goldleaf. This one has also been closed with a mantra by the 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.
So sorry, but Silver and Copper are not available at the moment!