1.size 18mm diameter *5mm with a 10mm down to 5mm countersunk hole 2.Coating NiCuNi or Ni 3 Grade N , M , H , SH , UH, EH We can manufacture all kind of size ring magnets from OD2mm to OD230mm(special size out of the normal scope, say extreme thin , thick or large magnet,please contact us for special arrangement), dimension tolerance: +/-0.05mm,magnetising orientation thickness up to 54mm). Our ...