I wear size 6 1/2 shoe and I ordered a size S/M (Shoe size 5 - 7 1/2) in these.  They fit me perfectly, but I seriously doubt they would fit someone who needs a 7 1/2; a size 7 is debatable IMHO, so you may want to consider the next size up.  Although the label reads "Tall Slouch..." they only come up to mid-calf (I think of 'tall' as being just about knee-high), so I thought I should mention that.
They have soft polyester soles with non-skid applications so they would Not be appropriate for outdoor use; but they are perfect for around the house and curling up on the sofa without a worry about damaging it.
The care tag indicates 'Machine wash cold with like colors, non-chlorine bleach if needed, and tuble dry low'.  I haven't tried washing them yet.  IF there's any change after that, I'll post again.