The IL stands for inline since this series of vertical machining centers is equipped with a 40-taper BIG-PLUS® dual-contact inline spindle. Inline spindles run smooth and quiet with minimal heat and reduced vibration providing better surface finish and longer tool life. The 10,000 RPM inline spindles have dual wound spindle motors for faster acceleration/deceleration and more torque. The IL machines also have bigger castings, faster rapids, and more standard features.