In the past, on some multi-day climbs, I slept under a tarp, with my quilt and air mattress inside a bivy sack. I also had other nights in a tent, in alpine country, with condensation wetting out my exposed quilt. Sometimes in shoulder seasons, my quilt isn’t quite warm enough. Then this year I discovered a great source of ultralight fabric. These were all motivations to try another project – an ultralight bivy, with options for bug protection and a cold weather liner. I finished it and have now tried it out successfully on a cold night.