Dirtbike and ATV / Quad chains by EK. The SRO line for a quality chain at a great bargin. The most popular for quads and dirtbikes. Most commonly 520's but smaller cc's like 85's can run the 4 series - 420 or 428. For hardcore racers the MRD6 non sealed motocross chains and the SH / SHDR for the smaller 420, 428 sizes. For extra strength durability and life the MVXZ is it! For more about the o-ring vs. no ring non sealed chain visit our chain selector page.