My grow box measures 1.4 mtr high x 2.4 mtr long x 1 mtr deep, I have 2 x 400 watt hps 1 x 600 watt hps and a 300 watt cfl in there ! I got 2 x 6 inch thermo controlled extraction fans and 2 x 4 inch inlet fans ! Upto yet not had any problems and turned out some nice lady's.