Isoblox Skull Cap with Impact Protection Young Adult Greater Protection than Foam Alone Products. Made with Impact Diffusion Technology Youth Medium- Approximately 18"-20" Head Circumfrence. Ages 10-14. Caps consist of uniquely-formulated protective plates that use a combination of dispersion and absorption techniques to diffuse energy upon impact with high-velocity objects. All skull caps have isoBLOX technology combined with 3/8" of specialized high impact padding. Caps are made with a stretchable, moisture-wicking material. Each cap also has an adjustable Velcro strap in the back to improve fit.