Feature： 1.Positive pull the chain, roller blinds down, reverse the chain, head only unlock, roller blind automatically up. 2.The system is equipped with retarder, and the roller blind rises automatically and stably. 3.Roller blinds can be stopped at any height. 4、By adjusting the number of pre tightening turns of boost spring, the rising speed of roller blindscan be adjusted. 5.1: 1.5 reduction ratio is adopted for the clutch making, which makes it easier to the chain. 6.The system is equipped with a limiter, and the roller blinds will automatically stop when it rises/ falls to a fixed position. 7. The clutch used to mental-core technology.