The main rubber contracts are RUXX0 1, RUXX05 and RUXX09. The main contract began to incorporate rubber continuity in the first five months, and withdrew from rubber continuity in the last two months. For example, the RU 1 105 contract became a rubber continuous contract in June 20 10. April of 20 1 1 is no longer a rubber continuous contract, so the main contract of April, May and June of 20 1 1 09 is Ru/kloc-0.