Flask Holder helps to prevent sample melt back. It allows a small Fast-Freeze Flask Bottom containing the sample to be placed inside a larger Fast-Freeze Flask so that the vacuum surrounding the sample insulates it from the room atmosphere. Compatible with inner flasks 7542300 (120 ml), 7542400 (150 ml) and 7542600 (300 ml) and outer flasks 7541100 (750 ml) and 7541000 (1200 ml). Stainless steel. Flasks not included.