A new design for calorimeter sample containers is described. The basic design is a hollow right cylinder with thin, glass membranes covering both ends. The membranes are intended to be broken out completely to release the sample contained within. The membranes are sealed to the container body with silicone rubber. The sample containers are easily fabricated, have highly reproducible volumes, and are surprisingly durable. Even though the membranes are fragile, the design permits considerable handling of the container with impunity.