28" Jacket Zipper, YKK #5 Aluminum Metal ~ Medium Weight ~ Separating ~ 578 Medium Grey (1 Zipper/pack) 28" Jacket Zipper, YKK #5 Aluminum Metal ~ Medium Weight ~ Separating YKK Color 578 Medium Grey (1 Zipper/pack) YKK aluminum zippers are made from the highest quality metal. Thoroughly tested to ensure strength & reliability. Aluminum Teeth.