Measurements are taken from corner to corner, with edges slightly curved based on precisely calculated radians. This design ensures that the shade sail remains tight and neat after installation, preventing sagging in the middle for optimal appearance and performance. Straight edges can also be customized. Durable Material: The shade sail is crafted from 100% 200 GSM HDPE (High Density Polyethylene), blocking up to 95% of harmful UV rays. The woven knitted fabric is breathable, allowing water and air to pass through while minimizing water pooling and wind resistance. UV inhibitors are incorporated during manufacturing. This material is designed to withstand sun exposure and is resistant to UV rays, water, and fading. Stainless D ring and Finished Edges: The edges feature heavy-duty double-layer reinforced stitched seams to prevent fraying and maintain the shape of the shade sail. Each corner includes a stainless steel D-ring for easy installation, with additional stitched seams at the corners to enhance the strength of the D-rings. How to Choose size & to Install 1: 1. Approximate how much area you want to shade. 2. Triangle square or rectangle depends on the number of existing poles, can also attach the shade sail with hardware kits to roof, tree, even concrete wall.3. Use cable wires to connect shade sail to hardware if necessary, if you don’t use cable wires, have a 0.5 - 2 ft space between D rings and poles, have some rooms for the hardware kits. Custom Sizes & Warranty: Our Custom-Size orders come with hassle-free 30-day returns and a 1-year limited product warranty. Your satisfaction is our commitment! 16' x 16' Blue Square Sun Shade Sail Canopy Outdoor Patio Fabric Shelter Cloth Screen Awning - 95% UV Protection, 200 GSM, Heavy Duty, We Make Custom Size