EK 520 Pitch SR Series Plain HD Chain. The EK SR heavy duty plain chain series offers the simplicity and low cost of a non-sealed chain along with excellent wear and anti-stretch characteristics. the 520, 525 and 530 pitch variants feature solid bushing which gives a greater contact area for the pins leading to a much lower wear rate and longer chain life.The simple construction of the SR series also makes them a great choice for racing. Every little helps as they say and with the low frictional losses of plain chains, more of the horsepower made by your engine is going to reach the back wheel. All the chains exhibit exceptional ultimate tensile strength, as well as light weight. The 520 pitch chain has an ultimate tensile strength of 35.6kN and weighs in at just 1.47Kg/100 links.