I think I have a Glacier Arc-Light in an XS-S. However the hip belt may be a medium. I can check. The old Dana sizing had separate tags on the pack body and the hipbelt. Also the sizing was XS-S, M, , L_XL because you could adjust the torso up and down with the velcro on the hipbelt.
This is a Bozeman made pack and is the same pack as the Terraplane but with fiberglass stays not aluminum.