single layer [thin] single-layer deepening [thick]] single layer [deepening and thickening]] double-layer binaural [thin] double-layer binaural deepening [thick]] double-layer binaural deepening [thickened]] double-layer four-ear [thin] double-layer four-ear deepening [thick]] double-layer four-ear deepening [thickened]] three-layer deepening [thick]] single-layer deepening [combination cover]] double-layer deepening [combination cover]] three-layer deepening [combination cover]] single-layer bakelite [combination cover]] double-layer bakelite [combination cover]] three-layer bakelite [combination cover]]

28cm