Secures in back of neck with hook and loop (velcro-type) closure. SIZING: Neck circumference, SMALL: 10” to 14” (note: very small as compared to like products), MEDIUM: 15” to 17” (most frequently ordered), LARGE: 18” to 20”, EXTRA LARGE: 21" to 23" Minimizes scatter radiation exposure to the thyroid area. Patented XPF® Technology contains no lead or heavy metals; non-toxic. Provides 0.5mm lead equivalency over the thyroid area and 0.25mm in the remaining areas. Machine washable; can be wiped down for cleanliness. Lightweight, flexible, fits comfortably around neck. Made in USA. Makes a great gift for a graduating medical student. Solid colors: Red, Blue, Purple, Turquoise, Poppy Red, Yellow, Black, Gray, Green, Orange and Hot Pink. (All fabric options.) All Thyroid Collar options. Visit the BLOXR website.