Once installed, switch flipped, light comes on very quickly, no flickering or buzzing, I use a quad configuration with 2 standard 48" mercury bulbs , 32 watts per ballast lamp (NOT LED) Make no mistake, they seem to be good quality at a reasonable price! Durability from Philips! No problems installing, used the same mounting screw as the old one, it was easy to remove and replace all in a row just fine I am currently recommending this to others.