LK6600 Treadmill The LK6600 is one of the quietest treadmills on the market. It features aluminium profiles with non-slip surfaces which help to prevent slips and falls during exercise. Moreover, the casing is made of hard-waring ABS plastic painted with the same technology used at the automotive industry. The HST Phenolic Wax System featured on the LK6600 Treadmill provides a low maintenance system, and eliminates the need of lubrication for an estimated period of 6 months or 1 year.