LED stands for light emitting diode and the 1157 style light bulb (bayonet) is a standard two light source bulb and has two pins protruding from the sides of the base of the bulb. When the light bulb is pushed into the socket a spring at the base of the socket pushes the bulb back against your downward pressure until you twist the bulb. Twisting the bulb allows the two pins to lock into slots in the side wall of the socket. This type of lamp is extremely useful in high vibration environments like on a trailer or for car and other vehicle tail lights.
This lamp is a fairly typical automobile light bulb. This bulb contains both a low brightness element and a high brightness element. The low brightness is typically the running or marker light, which can be on all the time. The high brightness element is the flashing, turn signal light, which is only on intermittently.
The incandescent 1157 is approximately 400 lumens on high or signaling. And on the low setting (running/marker lights) it is about 30 lumens.
So when shopping for an LED 1157 look for the equivalent lumens
Lighting Facts CRI Consider selecting light sources (light bulbs) that have a high CRI (color rendering index) like clearly explained in the chart above. This metric though possibly changing to CQS shortly (color quality scale) is still extremely helpful in areas where the true color of an object is needed to be known.
CCT CCT (color correlated temperature) is how you pick the actual color of the light being emitted. If you are thinking this a foreign concept you probably already have been changing this in your space if you ever used a dimmer.
Lumens Lumens are a measure of brightness or more technically a unit of luminous flux emitted from a lamp in all directions. The light flux falling on a surface one square foot in area, every part of which is one foot from a point source having a luminous intensity of one candela in all directions.