These tight-fit rigid feed, return and vent lines must be completed with a flexible oil line for connection to the oil pump. The very tight radius at the upper end of the lines creates more space for installation, as there is relatively little space to the heads, especially on Big Twin Flatheads with aluminum heads or Shovelheads in rigid frames. For use in rigid frames and horseshoe oil tanks with 9/16"-24 thread and 30° cone connections.