Circaid Compressive Undersock 15-25 mmHg Undersock. Undersock is designed to be worn under Circaid compression garments for additional comfort. The Undersock includes targeted and supported 15-25mmHg compression in the foot and ankle that helps make getting them on much easier. Undersock can accommodate nearly all patients with standard and large sizes. Specifications: Polyester, Nylon, Elastane Vendor: Circaid. If item is still listed, it's still available. $20.00 OBO! Thanks