37 double-layer small-hole aluminium alloy shutter sheet has the effective widthof 37mm and small holes of 20mm*2.3mm at the hook, enough for day lighting and ventilation.The distance between holes is 30mm. The shutter sheets are mainly usedfor the theft prevention and heat insulation of balcony and window, and alsoused as shade curtains. with the operative width not more than 2500mm. producing area:China payment:TT supplying capacity:1000pcs/month