Cultilite’s MH 4200°K – 400W is a single-ended metal halide grow lamp intended for vegetative growth. On the official HM product page, the 400W 4200 K variant is specified at 3.3 A lamp current, 103.4 lm/W efficacy and 42,000 lm luminous flux, delivering a photosynthetic photon flux of 545.6 µmol/s. The bulb uses an E40 mogul base and is compatible with standard magnetic or digital ballasts designed for MH lamps. In typical indoor cultivation with a suitable reflector, a 400 W HID light is used to cover roughly a 3.5 × 3.5 ft (about 1.1 × 1.1 m) canopy. This spectrum leans cool-white, supporting compact structure and strong vegetative development before a switch to bloom lighting.