One of the things that made the Herbalizer so popular is it's amazing versatility, the fact you can use it with either a bag or a whip straight out of the box is a massive plus over many other systems currently available. The standard medium sized bags that come with the Herbalizer are awesome and do a great job but if you want to go a stage further then these XL bags offer even more capacity for a huge amount of vapor. The increase means that one bag is big enough that you can either use them for a massive session for yourself or they are easily big enough that you can just fill one bag and pass it around your bros so that everyone can get in on the action without having to refill the bag. They are supplised in packs of 4 and are pre-built with the silicone valves already attached and ready to go, so one set should last you several months. All you have to do is unroll the bag and inflate it with the Herbalizer to fill it with vapor. Both the mouthpiece and the actual bags themselves are made of medical grade silicone so that they stay clean for as long as possible and there is also no annoying crinkling or crackling from the bag like with some other systems.