Size is only one number. Last shape decides how that number becomes volume around the foot.
Two pairs can share the same size label and still feel different because the last controls toe shape, waist, instep, heel, and overall volume.
Size is not the same as volume
Length gives the starting point. Width and instep decide whether the pair feels secure, tight, or loose once the upper wraps the foot.
Before production
Send length, width, instep notes, and a reference pair that fits well. The workshop can make a better recommendation when the context is specific.
