My Western Mountaineering Ultralite is a great sleeping bag but it has one design flaw. When the zip is fully closed, the draught baffle doesn’t fully cover the zip puller. Consequently, if you’re lying on your side, sometimes you get a cold zip puller dangling on your cheek. To prevent this, I’ve added a short fleece zip guard. Not the neatest bit of sewing, but hopefully it will work.
This is an issue on most of the sleeping bags I’ve owned. On the WM Highlite, I’ve added a zip baffle. On my Alpkit Pipedream and Cumulus Quantum, I added a snap closure. Yet again, you wonder whether gear is tested properly for these little irritations.