Q: Which zipper suits a sleeping bag?
A sleeping bag uses a size 5 or size 8 coil, two-way separating, with a bottom slider so the foot can be vented independently. The size 5 is normal on a three-season bag and the size 8 on an expedition bag where the shell is heavier and the zip is opened in the dark with gloves. An anti-snag tape or a stiffened edge behind the chain is worth specifying, because the slider catching the shell is the most common reason a bag is returned.
- Size 5 for three-season bags; size 8 for expedition bags.
- Two-way separating with a bottom slider.
- Anti-snag tape or a stiffened edge.
The usual pitfall is a one-way zip: the sleeper cannot vent the foot without opening the whole bag, and heat builds up. The second is a stiff tape that makes the bag curl when it is laid flat. Check that the two sliders park cleanly at the bottom and that the zip can be closed with one hand while the bag is inside a liner.