The liquid-tight insert contains a number of compartments that each holds one rack. Inserts are available for racks of various shapes and dimensions. The insert reaches all the way to the flat plate at the bottom of the liquid nitrogen vessel. When the vessel fills, the nitrogen level only rises in the space between the insert and the inner wall of the vacuum vessel. These frames are made for use with K-Series Cryostorage Systems. Racks must be ordered separately.