My "rooftops" series are all made from a bit of scrap copper I once upon a time received as a present; a piece of the roof of one of MITs old buildings, received when I still lived very nearby the campus. Wearing a piece of a university's roof won't actually make you better at math, but....
All colours on my copper are inherent to the metal- they are created without chemicals by carefully controlling heat and access to oxygen. Colour will last forever as long as you keep your piece away from chlorine, bleach, and other harsh chemicals. Hand-soap is fine. Sizing is quite flexible, but nothing is ever one size fits all; the size chart is based on the actual measurement of your wrist, so if you like things loose, size up, if you like them tight, size down.
Sizing is quite flexible, but there's nothing that fits everyone. We've made sizes for everyone along the gender spectrum.
X-small- best fit on a wrist 5.5 around. Will comfortably fit wrists 5-6 inches around. This really is very small. Small- best fit on wrist 6 inches around. Will comfortably fit a wrist 5.5-6.5 inches around. Medium- best fit on a 6.5 inch wrist. Will comfortably fit a wrist 6-7 inches. Large- best fit on a 7 inch wrist. Will comfortably fit a wrist 6.5-7.5 inches. X-large- best fit on a 7.5 inch wrist. Will comfortably fit a 7-8 inch wrist. XX-large- best fit on an 8 inch wrist. Will comfortably fit a wrist from 7.5-8.5 inches.