Use the bubble-free insert with the 3527 04576-05 40 mm XRF liquid cell to prevent trapped air from forming a bubble under the window film when the cell is upright. The insert is pushed into the cell before the sample is added and forms an inverted-cone shelf under which air bubbles can be trapped once the cell is filled and sealed. To use, simply push the insert into the X-Cell after it is partially filled. It is designed to fit into the major suppliers of normal optics XRF spectrometers made by Diano, Rigaku, and Shimadzu.