The problem is, getting to a base layer involves taking off at least a shell layer, maybe even a mid-layer. So we learn to grin and bear it. We wear shells that have zippers for venting excess heat, but sometimes we’re still over or under dressed beneath the shell.
Wouldn’t it be nice if your base layer could just zip off without taking your outer layers off? That’s exactly what Joe Tobiasson and friends thought, so they did a bit of research, found some flat zippers that didn’t feel like zippers next to skin and sewed up a few pairs of prototypes. As you might expect, it works, and I confirm, unless you’re a Princess you won’t notice the zippers.
What you might notice is some funny stares as you drop your pants to remove the layer underneath, or to add it back on. But at least you don’t have to completely remove your outer layer. Inevitably the hecklers will become envious at how fast and significantly you can alter your layering combination to stay dry on the climb, then warm at the top. If sweat is just pouring out, better to keep your base layer dry and replace it later when you need more insulation than to hope it dries out fast enough when you stop so that you don’t get chilled from convective heat loss on the windy ridge.
Wool or Synthetic, zip off baselayers