Solar heat sensing greenhouse automatic window spring opener. Made of metal iron and stainless steel, heavy-duty. The window opener automatically opens and closes as the temperature changes. Help to maintain the best growing temperature and prevents your greenhouse from overheating. Easy to install with clamps or screws provides, no batteries or electricity required. Specification: Material: Metal Iron, Stainless Steel Opening Force: 7-15kg / 15-33lbs Minimum Open at: 15-25 C / 59-77 F Maximum Open at 30 C / 86F Maxinum Open Distance: 45cm /18inch Overall size: approx. 33.5x5.5x3.6cm/13.19x2.17x1.42inch Package Includes: 1 Piece Automatic Greenhouse Window Opener Note: Colors might be different due to different monitor display. Manual measurement may cause slightly difference in size.