Great little device, makes knifes/screwdriver bits glow in seconds. Works as described, >100W for 12V, seems to be around 200kHz when idle - haven't checked it under load.

The unit oscillates with frequency 157 kHz according to my scope. At 6.5 V the current 1.65 A goes across 1 mm wire coil (12 turns diameter 1.5 cm). After insertion of thin steel wire the current rises to 3.5 A and red glow emerges fast. Under these conditions the unit can run for an infinite time - it gets warm, but the active cooling is not actually necessary. I haven't tested it at higher voltage/currents yet - anyway it seems, it's a good, reliable product, professionally assembled with caution.