Maintenance-free 50 roller chain is generally utilized in applications where maintaining the roller chain is difficult and or impossible. Also depending on the chain used, in applications that are dusty or dirty. We stock a wide array of problem solver/ maintenance-free chains.
#50 self-lubricating chain:
Self-Lubricating chain utilizes an oil-impregnated sintered bushing to continually disperse lubrication within the chain its self.
#50 O-Ring Roller Chain: 
O-Ring chain utilizes o-rings within the chain to keep lubrication in while keeping contaminants out of the chain.
#50 X-Ring Roller Chain:

X-Ring chain is the same concept as the O-Ring chain only with an additional wear resistance factor.