On steppers, a transmission is also known as speed reducer or gearbox. Works with Stairmaster 4000PT, 8G StepMill, and SM5 StepMill. Compatible to OEM #SM22434, #SM25497, #050-0130, #711-3334, #711-3334-KT, 050-0002. Comes with a 1 Year warranty from date of invoice.