Nickel or customized
+-0.03mm to +-0.05mm
20x5mm with 12-5mm countersunk hole：
20x5mm with 12-5mm
Ref drawing for Countersunk hole :
These magnets are very strong magnetism, which should be handled carefully. Do not allow children to play with them unsupervised
Keep the magnets away from pacemakers and magnetic storage devices such as mobile phone, bank card and computer etc.