AMS Flat Plate drives have been around for decades and continue to be a top selling line.  When properly installed and regularly maintained, these drives can last decades in even harsh marine environments.  The hoist is sold with either a 1/2" aluminum or 1/4" galvanized steel backing plate (the 8500 not available with aluminum).  The 6500 and 8500 models feature a ductile iron bull gear for extreme tensile strength and a HD bronze worm gear.