What's the Difference Between the Polycom Lift Kit and the Extender Bar for Handset Lifters?

The Polycom lift kit verses the extender bar which comes with all lifters..

"The Polycom lift kit acts like a lower lip, this is if phones do not have the lower lip and the receiver slides down when lifted. The extender bar comes with all lifters and helps when there is a curved edge on the left side of the phone"