My husband has tried various other brands of socks ,none of which
remotely resembled the L/XL I chose for him.
He finds Posey socks comfortable and true to advertised sizing.

JAY J3 Backrest
Height: Lower Thoracic: 6.5", 8", 9.5" / Mid Thoracic: 12", 13.5", 15" / Upper Thoracic: 16.5", 18", 19.5" / Shoulder Height: 21", 22.5", 24"
Maximum User Weight: 12" to 20" widths: 136kgs / 22" to 26" widths: 226kgs
Support Level: Low Thoracic, Mid Thoracic, Upper Thoracic, Shoulder High
Cover Type: Air Exchange / Microclimatic
Contour: Shallow, Mid Contour, Deep Contour, Mid Deep Contour and Posterior Deep Contour