There are three different types of bulbs, well tube lights anyways. t12s t8s and T5s. the T12 and T8 can use the same type ballast while the T5 needs a special one. the lower the number the more lumens the light puts out. The blue end of the spectrum is more for vegative growth while the red end of the spectrum encourages flowering. you can however flower a plant under a veg bulb. the end result may not be as great but you will have buds

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BIG BOB