After installed this controlled automatic vent opener, your window will be a self opening . It is solar heat sensitive that open the vent when weather warms up and then closing when it cools down. Really works well in maintain the greenhouse within the preferred .

Features:
Compared with the spring vent, the double has thrust , more solid, and much .
The double spring vent opener can be closed manually.
Elongated cylinder with paint spraying, weather resistant.
Solar heat sensitive vent opener, automatic stretch or shrink the vent while the is changing.
Stainless steel accessories would last long use.
frame looks more lustrous, and rust-proof.
Easy to install, universal fit for all frame greenhouse.
Auto-opening is adjustable from 15-25℃(60-77℉) by turning the cylinder. (Clockwise for higher, counter-clockwise for lower)
Maximum opening at about 30℃/86℉(depending on adjustment and load).
Suitable for the vents weighing up to 7kg/15lb.

Specifications:
Material: +SS
Item Weight: Approx. 376g / 13.26oz
Package Weight: Approx. 439g / 15.49oz
Package Size: Approx. 38 * 9.5 * 4.5cm / 14.96 * 3.74 * 1.77in

Package List: H20972
1 * Vent Opener
1 * Package of Accessory
1 * Manual (English)

Note:
Do not heat to more than 50℃(122℉).
Do not dismantle the cylinder.
Cooling the cylinder for 24 hours before installation.
The maximum angle of product opening and closing is 45°.