One of the perceived main attractions of a fixed gear bicycle is low weight. Without the added parts required for a fully geared drive train—derailleurs, shifters, cables, cable carriers, multiple chain rings, freewheel hub, brazed-on mounting lugs—a fixed gear bicycle weighs less than its geared equivalent. The chain itself is subject to less sideways force and will not wear out as fast as on a derailleur system. Also, a fixed gear drivetrain is more mechanically efficient than any other bicycle drivetrain, with the most direct power transfer from rider to the wheels. Thus, a fixed gear requires less energy in any given gear to move than a geared bike in the same gear.