The "cracker" is like two pieces that screw together with a pin inside. You put the canister in and screw it all the way closed which pops the canister. There is a whole on the actual canister its self where the gas come out of. Easily, a rubber tube can be placed over the end and ran into a mini rubbermaid or other holding device that is rubber (so that the opening where tube goes in is sealed) that holds your mice. "The mice chamber".