Parallel shaft gears offer optimum reliability and lower MTTR and are preferred for ease of maintenance and minimum components. Parallel axes are the most common gear arrangement, consisting of a meshing pinion and gear. Parallel arrangements can be simple, or compounded with other parallel gear sets to obtain high gear ratios. The conventional way to describe such a gear is ‘double increaser’ or ‘reduction’ or triple increaser’ or ‘reduction gear’. Parallel axis gears can use spur, helical, double helical or herringbone elements.