Frenergy stocks a range of Neodymium Block magnets in varying Grades of strength to suit your particular application. This N38 Grade magnet carries the additional “M” suffix which indicates a moderately higher tolerance to heat (up to 100℃) than standard grade (up to 80℃ ) magnets. Temperatures above this limit will cause a gradual loss of strength or even total demagnetisation. Extended exposure to heat or Curie temperature levels can cause permanent loss of magnetism to the magnet but over short periods the magnetism will be restored as the temperature returns to ambient levels. This product is manufactured with a central hole that can assist with mounting or attachment needs or for more convenient locating on pins or lugs. Placed on non-ferrous rods, the magnet can slide and interact with magnetic fields or metallic material in devices like gauges and sensors used in industrial monitoring systems. For hobbyists or general domestic use, the holes provide an attachment point for use with wire, thread or cable ties.