The lamp is that max. E27 - 60W should be possible. That's what I built so because 40W would be probably a little bit. Unfortunately, the pre-drilled holes fit not to the distance of the holes in the flush-mounted box in the ceiling. But this one has the appropriate tools ... What does not fit is made to fit. The built-in ceramic terminals are not exactly inspire confidence. Looks all Made in China .. but is it Made in Austria.