Bottom of Climber Extension - Bronze Leadscrew Nut (turned down) inside a 1" OD x 0.028" wall steel tube inside a printed square linear bearing, all held together with four 6-32 x 7/16" SHCSs which thread into the Leadscrew Nut. This all travels within a 1-1/2" x 1/16" wall 6061 Al square tube.