Bosch Insight 4921 Wiper Blade - 21" (Pack of 1) Delivers improved wiping performance and longer life due to Bosch patented internal tension spring which provides consistent pressure Quick and easy installation. Covers: Pin arm (4.8mm & 6.35mm), Hook arm(9x3 & 9x4) Provides consistent high speed performance due to robust integrated spoiler Less snow and ice buildup due to enclosed hybrid construction which minimizes gaps in joints Premium hybrid design utilizing Bosch beam expertise, unique in the market