API SEC-9 GRADE BENTONITE Suspension Properties Viscometer dial Reading at 600 r/min. Minimum 30 Yield Point/plastic Viscosity Ratio Maximum 3 Filterate Volume Maximum 15.0 cm3 Residue of diameter grater than 75 micron. Maximum mass fraction 4.0% API SEC- 11 GRADE BENTONITE Suspension Properties Viscometer dial Reading at 600 r/min. Minimum 30 Yield Point/plastic Viscosity Ratio Maximum 6 Filterate Volume Maximum 16.0 cm3 Residue of diameter grater than 75 micron. Maximum mass fraction 2.5%