Made of firm materials with adjustable chin strap. Made of Plastic.Each helmet is approximately 11.5 inches long, 9 inches wide, and 6.5 inches tall.Opening allows up to 61 cm circumference or 24 approximately inches. With strap closed approximate neck/head fit is 27-28 inches fully extended on the straps. Fits Snug.Halloween military prop for costume and novelty use. Not a safety device.Great Accessory for Costume For Adults, Army Reenactment, Theater and more.