All massage recliners have an S-Track (sinusoidal or "s" shape of the spine) on which the massaging rollers travel up and down the spine. The S-Track roller travels from the top of the neck to the low back. However, the newer "L-Track" technology extended that track to travel all the way down, under the buttock to the hamstrings. This allows for an additional 30% more body area to benefit from the various massaging techniques delivered by the rollers. Depending upon your wellness needs, you may prefer the L-Track design for your perfect massage.