This is the US 2-quart olive drab plastic collapsible canteen (reduced sloshing noise as it collapses while emptying) with special cap that allows you to utilize the Type M hydration systems of US M17, M40, and M45 gas masks. Can also be used as a normal canteen.  This listing also includes an insulated nylon/fleece cover with canteen and special cap for US military hydration systems such as the US M17, M40, and M45 gas masks with a Type M connector for canteens and bladders.. Two quart potable water capacity. Canteen plastic color is olive drab.  If you have a preference on the style of cover you can request the one you like, but we have no promise that all would be in stock. These items may have been previously issued and may show signs of use, but are in excellent condition. The connector cap will not work with the Israeli or Soviet masks on this website, nor will it work with any mask with a built-in hydration system. Will not work with a US M50. The special cap does not alter the normal functioning as a canteen, you can still use it as you would any canteen. See other listings for more photos of the canteen and cap and the applications with a gas mask hydration system.