Okay, I just got a couple pair of L/XLs...
Okay, I just got a couple pair of L/XLs (verified as printed on the sock). I wear a 9.5 US shoe. The size chart says L/XL should fit a 7.5-9.0, but these are about an inch too long for my foot. I've never had anything from Castelli run large. I'm planning on sending them back in for the S/M, but I'm worried they will be too small...size chart says 3.5-7.0! Any thoughts?
You should be fine with the S/M socks.
I'm a US 9.5/10, I bought the L/XL and the heel cup marking (where sock is different color at heel) ends up covering my Achilles tendon when pulled up tight enough to prevent bunching around my toes. I bought the Medium and had a perfect fit.
Castelli is bizarre fit wise. Socks are typically much larger and shorts/jerseys much smaller. I'm a huge Castelli fan, just takes trial and error trying to get the best fit. Don't get me started on the way Castelli full zip jerseys vs. 1/2 zip jerseys fit....