... *30, 14*20, 14*25,16*25,16*30, 18*30, 20*20, 20*25, 20*30, 24*24, 24*18, 25*25, 25*308 ... ) Sound absorption: Germany soundtex, MRC0.65~0.8 10) Workmanship: Compression moulding forming The product's charscteristic: 1.For air return application ...