Made of leather, these helmets are light and protective for when you're driving your tank. 
These are a one-size-fits-most, so as long as you don't have the head of a literal giant, you should be fine. 
These helmets would have been used for tanks such as the Swiss Panzer 61/68. 
 
These are used so they may have stains, fading, fraying, and scratches. But otherwise, these are all in good shape.