Why is it necessary to use a resistor? are the leds that delicate?

I put a red multi LED light in my boat last year I just wired it normally into the 12v system, (maybe it had a resistor built into the plastic case?)

thanks,
Robert


Ps. Looks great BTW! In my jeep I use a flashlight to peer at the last 2 working gauges.

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Cheers,
Robert