A groove is present on the inside shaft of all of those that I have handled, which is where the plastic is injected. When we were racing on dirt tracks, we would experiment with different lengths of steering shafts; nevertheless, we did not worry too much about the broken injected plastic so long as the shafts did not come apart while the car was in motion. We hastily verified that the columns could collapse doodle jump and would not be separated under typical usage, and then proceeded. We were more worried about the car's wreckage and the possibility of the column shafts being torn apart in a severe enough crash.