What is the Pro Care Thumb SPICA™? A lightweight thumb support with firm outer shell & soft terry lining for thumb immobilisation following injury. When can I use it? For protection of thumb arthritis & thumb tendonitis. Which size do I need? Small/ Medium fits most women & smaller men. Large/X-Large fits most men & larger women. How does it work? The hard plastic shell completely immobilises & supports the thumb. This relieves thumb pain by taking the strain off the ligaments & tendons of the thumb & wrist. The perforated shell means that the Pro Care Thumb SPICA™ is strong whilst being lightweight & well ventilated. The soft terry lining improves comfort & the whole support is held in place with two Velcro straps.