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.

Configura Advance Black Profiled Headrest
Suitable for users with reduced head control. Fits over the shoulders.
Configura Advance Profiled Headrest Specifications:
Colour: Black
Fabric: Vapour permeable
Attached using 2 poppers and is easily removed
Suitable for users with reduced head control