The installation instructions (from 50 you need a magnifying glass ....) has left some questions unanswered. As before, I am not sure how because the upper part can be screwed to the lower part (outer sleeve). I have come up with a mounting system that but the floor lamp still does not prevent to twist.
I have installed a 5 Watt LED, which delivers beautiful and energy efficient lighting. This hot neither glass nor illuminant.
Price and quality are perfect, expensive floor lamps not pay off. Dear every few years an exchange, if necessary.