4K - 4000 Kelvin: Neutral Metal Halide
Best single source for plant growth, producing shorter, bushier
growth than 3700 Kelvin and color rendition. Used in general
plant lighting.
3.7K - 3700 Kelvin: Softer Metal Halide(coated)
This coated lamp is used in general plant lighting and for more
rapid growth than 4000 Kelvin produces.
3K - 3200 Kelvin: Warm Metal Halide
Highest photosynthetically active radiation (PAR) value of all HID
lighting for all phases of plant growth. PAR watts account for the
nutritional value of light and are a direct measure of the light
energy available for photosythesis.
2.7K - 2700 Kelvin: High Pressure Sodium Lamps
Redder color mix, used for propagation, blooming, supplemental
greenhouse lighting.
the mh is better suited for the veg groth where as the hps is in a better range for flower