McFarland Standard for 18mm glass tubes. Set of 0.5, 1, 2, 3, 4, 5 McFarland Turbidity Standards. Type: BaSO4. Life about 4 months on delivery. Lead time 4-6 weeks The BaSO4 standards must be shaken well before use. We recommend using vortex V-1 plus, which provides intensive mixing.