1) Product Name: permanent magnets 2) Ring ferrite magnet is widely used in speakers Product Name: permanent magnetsFeatures:Size: Outer diameter: max. 280mm, height: max. 40mm Properties: Y20,Y25,Y30,Y30BH,Y35 (China Standard) C5,C8,C11 (U.S.A.Standard)Applications: Ring Magnets are widely used as various speakers (home audio and car audio).