The Makita 628935-9 Field HM1304B provides the magnetic field required for the motor to operate in compatible demolition hammer equipment. It works with the motor's electrical system to support the conversion of electrical energy into mechanical movement. This replacement field is designed for use during power tool maintenance or repair when the original component is worn or damaged. ... https://www.wholetoolbox.com/makita-628935-9-field-hm1304b/628935-9.html