How to know the bad products?

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Is there a way to know the bad products only by appearance?


Only by look, do not judge the product. However, as a basic concept of lighting, You must be careful about LED lighting commercialized by using the LED package called "bullet-shaped".. Because bullet-shaped illuminance becomes very high, it is very effective as a lighting to see, such as in bulletin boards and traffic lights. However there will be no enough spread of light in an entire room as supposed to be and hence it is difficult to take advantage of it.