Electric roll up unit or motor can  achieve the rolling up and down of greenhouse films. Then ventilation the

greenhouse.and it produced by our own company and has beed added some newly  designed factors by our designer.It 

has alot of advantages such as  light in weight(lighter than other like produces ) ,water proof,dew proof,easy to

use(three sides to install the accessories),high pricision(two power swichs in series can make the pricision

control more accurate),long in useful time(ten years)etc, and the price is much lower than like produces from

other countries.