The Chinook Powerglide Windsurfing Sail: Performance, durability, and light-weight built into one sail. Majority of X-ply material combined with Dacron is very light yet extremely durable. Endo-batten seam shaping helps to create a powerful sail that is tunable with screw-adjusting batten tensioners. Designed for demanding recreational sailors. Size: 4.0, Boom: 150-153, Luff: 376.