A dimension representing the largest diameter workpiece that a lathe can rotate. The 7x10, 7x12 and 7x14  mini-lathes all have a 7" swing, meaning that the maximum size workpiece that can rotate without hitting the bed is 7" in diameter. A related dimension, Swing Over Carriage or Swing Over Cross Slide, is the maximum diameter workpiece that can rotate over the cross slide. This is about 4" on the 7x lathes, so any workpiece longer than about 3" cannot be larger than 4" diameter.