@hike101 thanks for reaching out! This is actually exactly what we would recommend when you're between sizes and want to try on both - you can order both sizes, select store pickup at your closest REI store, and head in when they have arrived. You can then try on both sizes and return whichever doesn't fit! Looking at the reviews, they seem to be running pretty true to size, so likely the 10.5 will fit (although may feel a bit snug at first), but you can certainly order both sizes to be sure; hope this helps!

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