Q: Which zipper is right for a hardshell jacket?
A hardshell needs a size 5 PU-coated waterproof reverse coil on a coated tape, open-end, with sealed top and bottom stops and a storm flap. Alpine cuts above roughly 80 cm body length should use a two-way slider so the jacket can vent from the hem while a harness or pack belt stays fastened. Pit zips take a size 3 waterproof coil, and pocket zips a size 3 or 5 depending on the load the pocket carries.
- Size 5 waterproof reverse coil for the front; size 3 for vents and pockets.
- Teeth face inward so the coated tape presents a flat, matte surface.
- Every stop and end must be sealed, not just taped.
Puncturing the coating is the classic pitfall: the needle opens a channel and water wicks through the tape even though the shell fabric passed its hydrostatic head test. Vents sewn without a flap are the second failure, because rain runs straight into an open coil. Use a fine needle, a sealed seam and a flap that overlaps the slider by at least 10 mm.