The AlAn Screwed and Glued Frames had a habit of cracking at the 'lugs' .. the Italian company now makes a welded aluminum frame .

its a tapered thread like plumber steel pipe 1 RH thread the other end LH so turning the tube pulls the lugs together onto the tubes

I transferred a lot of my 80's Alan Components to a steel frames in the 90's.. Still have the 25.0 <C> super record seat posts (will sell)