stop/tail light bulb wattage question

1157 27/8 W is the bulb I need, but I was wondering why the wattage is 27/8. Whats the purpose of the backslash. Can you get bulbs rated at either 27 or 8 watts?

Or I was thinking when you hit the brake, the light draws 27 watts of power and while it's simply on it only draws 8 watts of power.

Also is it important to make sure it is a 12V bulb as well? I have a feeling 1157's are universal to these ratings.

 

The 1157 is a dual filament lamp. The 27 Watt part is for stop/turn and the 8 Watt part is for taillight.

If you buy an 1157 lamp, it's rated for 12 Volts nominal, 27/8 Watts. You don't need to worry that it's the wrong voltage.