Sl Track Massage Chair is the most advanced roller track than S Track and L Track. S track is the roller track that does deeper massage on the neck and lower back where more curvature has than just straight up and down track. SL Track is an extended version of the S track with curves that L track massages all the way down to the buttock up to 140 cm. So this massage chair is the best in the market with premium advanced features, So what are you waiting for try our Premium Gebco Massage chair at https://gebcomassagechair.com/