... gear motor, drive shaft, rail vent rack and pinion, shaft supporter, wheel supporter, handspike,supporting wheel,rack and pinion connectors etc. It is mainly ... alternate vent system.NameModelSpecificationAlternate Vent PinionCLJC-1---Alternate Vent RackCLJC-1050L=1050 mmALternate Vent RackCLJC-1200L=1200 mm Rail Vent Rack and Pinion