Bulbs used in Lightforce Lights have been carefully selected to ensure maximum performance and durability. This is done by measuring and qualifying the efficiency in converting watts into *candlepower. This combined with the superior Lightforce reflector is what creates the Light output that has made Lightforce famous. The bulb filament size and shape combined with the reflector design determine the concentration of a focused beam. The shape of the filament will determine the type of Beam, e.g. a vertical filament (VF) bulb will give a circular spot beam, whilst the horizontal filament (HF) will give a slightly oval spot.