How so, do they run big or what?
I have worn both medium and medium short 3.3 Zipfree. If you look at the size chart, they’re almost identical:
But the arms and legs on the M are significantly longer and the shoulders are more broad. They’re really not as close as the chart indicates. I’d say the M is more accurately for someone 5’9-5’10”. Funny thing is their comment about their model, he’s off the chart for a medium:
I’m 5’8” 175 and wear the MS. Arms and legs are just right. It’s snug at first but pretty good fit. So again, I’m off the chart. I’d say MS is for 5’6”-5’8” 160-175
Also, I’ve had flushing issues on both the M and MS. It’s the cord and cord lock. I swapped the cord lock and it helps, but not great.