Prices are as marked; discounts vary by size. Sales items are final and cannot be returned or warranted. Ideal Core Warmth and Performance. The Infiniti series is the work horse in the Xcel lineup. It offers the perfect balance of warmth and stretch. The Radiant Rebound core locks out cold, while rebounding your body’s heat within. ThermoLite IR is used in the lower interior for added stretch and warmth. The exterior has Channel Flex upper and Ultra Stretch lower.