These magnetic discs can be used with our mini plastic gearmotors (extended motor shaft versions only) as part of a quadrature encoder system that offers 12 counts per revolution. They are 2 mm thick with an outer diameter of 9.7 mm and an inner diameter of 1.5 mm. Appropriate Hall Effect sensors, such as those in our magnetic encoder pair kit for mini plastic gearmotors, are required to complete the system. These discs are bulk-packaged and must be ordered in multiples of five.