We obsess over fabric at the store. Customers ask about Gore-Tex vs Pertex vs eVent. All valid questions. But here's the secret: fit matters more.
Why
A shell that's too big has big air gaps. Those gaps fill with wind and rain. Your "waterproof" shell now has cold air pouring in at the cuffs, neck, and hem.
A shell that's too small restricts movement. You hunch. You sweat more. You tear the underarm seam when you reach for a rock.
The right fabric in the wrong size performs worse than the wrong fabric in the right size. Every time.
What to check
Raise your arms overhead while wearing the shell. The hem should stay at your waist, not ride up to your ribs. If it rides up, too short.
Cross your arms in front of you. Shoulder seam should stay on your shoulder. If it pulls across the back, too small.
Zip the collar all the way up. It should come to mid-chin, not under your lip. Too high and it chokes you. Too low and snow or rain gets in.
Put your pack on. Shell should still move freely with the pack on. If the straps pin your shoulders and you can't move, size up.
Sleeve length
Should cover your wrist bone when your arms are at your sides. When you reach forward (climbing move, hiking pole), should still cover most of your wrist.
Gloves vs sleeves: sleeves go inside glove cuffs if the glove has a gauntlet. Over the glove if it doesn't. Design your layering for the gloves you actually own.
Hood
Should rotate with your head. If you look left, the hood looks left. If it stays pointed straight ahead while your head turns, it's not fitted well. Draw the hood closures tight and re-check.
A hood that doesn't move with you is worse than no hood at all. You lose peripheral vision and you get rain down your neck.
Brand differences
Patagonia runs long in the torso. Arc'teryx runs slim. Outdoor Research is roomier. Rab is European-cut (narrower shoulders). These differences matter more than fabric family.
Try three shells in the store before you buy. It's the only way to know what fits your body.
