New bellows design incorporating edge-welding technology replaces the old resistance weld design, resulting in 30% longer life and vastly improved linearity - a key failure mode of the original design where spring rate increases with bellows deflection (movement). Couple that with controlled and repeatable manufacturing processes and the result is linearity so consistent there may be no need to match range springs in calibration - and unit-to-unit calibration is virtually the same in every system.