Level 1 (range ~ 0.05 g/l corresponding to ~ 3.0 µmol/l)
Level 2 (range ~ 0.12 g/l corresponding to ~ 7.5 µmol/l)
Level 3 (range ~ 0.28 g/l corresponding to ~ 17.0 µmol/l)

The controls are only produced to order.
Minimum quantity is 5 litres per level.