... Light weight,Good strength,Good toughness use for working of construction, aerial working Anti-shock Material: ABS, PE, PP, ... okRib: one rib, two ribs and three ribs on the top of shell could be doneLock type of back ... adjust is okSpecific: Withstand a weight of 5kgs falling on to it if dropped 1 mete, can be used ... free to contact me . hard color safety construction, aerial working helmet or head wear