Mine is six spiral BLBs on 2ix-inch centers. The box itself is MDF, with a plywood top. Flap front door, small exhaust fan. I have a switch to turn the lamps/fan on and off, and my practice is to leave it on for the entire printing session - the warmup time of fluorescent bulbs is a consideration if you use a timer to control exposures by switching the lamps on and off, so I just use a kitchen timer to measure how long a print has been 'in the oven'.
The box itself takes up a lot of counter space, but it makes a great base for the dry mount press.