Technical data Spec. D* H* T( mm) Number per m³ Bulk density ( Kg/ m³ ) Surface area ( m² / m³ ) Free volume ( % ) Dg25 5-ring 25* 9* 1.5* 2 170000 90 195 82 Dg47 9-ring 47* 19* 3* 3 32500 111 185 88 Dg51 9-ring 51* 19* 3* 3 23500 103 180 98 Dg59 12-ring 59* 19* 3* 3 17500 72 150 92 Dg73 12-ring 73* 28* 3* 4 8000 80 127 89 Dg95 18-ring 95* 37 * 3* 6 3900 78 94 90 Dg145 20-ring 145* 48* 3* 6 1100 48 65 95