I had a melt down of my twin bulb 40w florescence fixtures last week. First one fixture would not start - ballast shot. Then a second one and a three one had one bulb burn out and replacement bulbs would not light either. With my poor eyes straining to see I finally went looking for replacement LED bulbs for my fixtures. Before I retired, the boss decided to put some money into LED lighting so I had an idea how this would work. The only problem was the cost. Bulbs at work in a large order cost $23 buck each. I found a site (Green Light Depot.com in Norcross GA) with 18w T8 bulbs for $7.59. I could not believe my eyes. Ordered up two bulbs just to give it a try. T8 will be direct replacements for T12. Other problem is some LED bulbs are compatible with ballast or bypass lights, some are bypass only. Ones I bought were bypass only, but with the ballast burned out that is the one I ordered. Rewire required that both pins on one end are line-in and other end both pins are neutral. Simple enough and boy are they bright. They do come in 6000K, 5000K, or 4000K. Mine are the 6000K. I am impressed. Now all I need to do is save up to replace all the rest of my bulbs (8). I got to say that I would not think 2 - 40w florescence bulbs (all be it that they are cooler temperature bulbs, probably 4000K or even 3500K) could be replace with 2 - 18w LED bulbs but I am a believer. Just thought I would pass this along to fellow woodworker if you are considering new lighting in your shop.