The circulation of IZ is 8.000 copies. More than 7.000 addresses have been classified according to the SBI code of the chamber of commerce in the Netherlands.

%      Code  Type of company Employees
68% 45331 plumbers, fitters, installers of sanitation 4.800
32% 45332 installers of heating and air handling units 2.200
The remaining addresses have not been more closely subdivided.