A suspension system for a rail car has at least two undercarriage members and at least one equalizer bar removably and pivotally secured to and between the two undercarriage members. An exclusive socket detecting part detects whether a socket connected to the plug is an exclusive socket for the plug. The instruments and methods disclosed provide improved visualization of the surgical field and enhanced precision of placement of spinal fusion implants between vertebral bodies. The first spacer arm may be configured to contact a pressure side surface of the rotor blade. The slit runs in a direction of the width of the gas bag.