-lightfoot
correct, by 'bar end' I am reffering to the handlebar extensions often put onto mtb flat bars to gain an additional hand position.
not to be confused with the shifter itself 'bar end shifter' aka 'barcon'(less ambiguous)
photos are difficult...

-willis
Actually, I purchased those exact same bar ends from that same seller for my 'prototype' attempt
conclusion; cheap bar ends are indeed steel, but have inconsistent tube quality -one side fit fine, the other had slightly thicker walls and needed to be reamed out
For final configuration I used nicer bar ends, which were steel by virtue of their manufacture age (very thin wall cro-mo); not modern cheap steel ones(hi-ten junk)



So, it is advised to use bar ends from the mid-eighties made of good quality steel for best results. Unfortunately the ebay market for such a thing is not well demmanded. nowadays the bar ends are aluminum, carbon, or ergonomic(not round tubes)

Alternately, at performance bikes I saw Forte' OS (oversized) bar ends, which are aluminum but are larger diameter; this will likely work but you will have to put up with the obtrusive clamp area (aluminum stuff tends to be fatter than steel)