Of the 'replacement bulb' type LED's, the 19 LED variant has 19 rear facing LED's, while the 24 LED type has 18 rear facing and 6 radially mounted. I tried a 19 LED bulb in my 900ss, but found that as there was no reflected light, it wasn't really bright enough. With the 24 LED type, there is plenty of light hitting the reflector and the effect is similar to a standard bulb but with the advantages of LED's.
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