Oppo: Rigid Adjustable Neck Collar OP4090. Semi-rigid support for use in soft tissue damage, osteoarthritis and whiplash injuries. Completely adjustable height to provide flexion or extension positioning Vinyl-covered foam padding for patient comfort and easy cleaning. Size: Measure around the circumference of the neck: 34.3-40cm Small, 40.6-46.4cm Medium, 47-52.7cm Large, 53.3-59.1cm X Large.