PERFECT MAGNETS Ferrite Ring Magnet/Ceramic Magnet With 13.5mm O.D. X 5.5mm I.D. X 2.5mm Thickness With 1 Ns Coin (50Pcs) TRIOMAG Ferrite / Ceramic Anisotropic Ring Outer Diameter : 13.5mm Inner Diameter : 5.5 mm Thickness : 2.5mm Grade : Y30, Set of 50 pcs