... disc permanent ndfeb magnet 1.grade: N35-N52,(M,H,SH,UH,EH) 2.ceritfication:ISO9001:2008 / SGS 3.good service ... of the high anti-corrosion coating could be more than 1000 hours5) low weight lossPCT:130c ,humidity 100%,vapor pressure 2 ... . N42 disc permanent speaker ndfeb magnet N35-N52,(M,H,SH,UH,EH)