The Renson ZipShade® is the ultimate value in exterior sun protection since it performs several functions, including sun, wind, and bug protection. The secret is in the locking zipper side channel. Originally created for Japanese bullet trains, when speeding though tunnels pushing a shock wave of air that would blow roller shades out of their side channel. Now perfected for exterior use, the zipper fabric lock keeps the shade flat and smooth, and seals the edges keeping bugs out. It can even keep golf balls from breaking windows.