The nicotine content varies per filter group.

They are defined as:-
High = 16mg
Medium = 11mg (equiv. to Marlboro Red nicotine content)
Low = 6mg (equiv. to Marlboro Light nicotine content)
Non = 0mg (Pure Steam and flavour)

Example
As each filter lasts on average as much as 30 cigarettes, the nicotine content per medium level filter would be for example 0.35mg/cigarette, this is equivalent to Marlboro Reds.