well i emailed freds frames and all he said was......."Hello the only information I can give you is on my web site . Freds Frames. "

this is on the website "Also returned to the line up are his rigid front ends, which were popular in Southern California the late 60's and 70's. These front ends start with 20" over sizes. "What makes it work is that there's chrome-moly on the inside, which acts as a spring. Chrome-moly's got like a memory where it springs back into place. It flexes; it bounces back. The rigid front end is the best riding front end I've ever ridden."

so chromoly on the inside...........inside of what?? steel tubes or what? thats all that was said.......gonna be tough to figure out. guess ill just buy some tubes later on one day and try it.