... disc permanent ndfeb magnet 1.grade: N35-N52,(M,H,SH,UH,EH) 2.ceritfication:ISO9001:2008 / SGS 3.good service ... however). Pretty strong hold between two of these even with a couple of mm in between.Cons: Would like thicker (and ... . N42 disc permanent speaker ndfeb magnet N35-N52,(M,H,SH,UH,EH)