Well they make chains for motorcycles street and dirt ranging from about 428-630 the most common on streetbikes are 520, 525, and 530. The 530 is going to heavier duty, and usually have a higher tensile strenght. The 530 is also a considerable difference in weight compared to the 520. well if you think about it, the chain is wider, so the sprockets are going to have to be wider, which in turn they are going to be heavier also. all this weight we are talking about is Rotating mass, or Unsprung weight, which is weight that is moving. Unsprung weight makes a bigger difference because it feels like more weight than it actually is. If you hold a 520 and 530 chain, same number of links you can feel the difference in chain weight, well if its 1 lb of actual weight difference, just think about how much weight it will feel like while rotating. Most people go to a 520 kit because. #1. 520 is more readily available. #2. Because your saving weight and rotation mass. and you can find 520 chains that are going to have a tensile strength very close to 530 chains. Unless you are on a 1000, you don't need to worry about the strength of the chain. Hope this helps, might be too much reading or not very clear, just let me know.