Nitro double heavy roller chain is a two wide/row chain that is commonly referred to as "duplex roller chain". The heavy duty series uses thicker link plated over a standard ANSI roller chain. Thicker link plates significantly increases the fatigue resistance and overall strength. All of our double heavy series roller chain is manufactured to conform to ANSI B29.1 industry standards. Chain manufactured to these ANSI standards ensure that these are compatible with any ANSI sprockets.