Coating bonded to a flexible fused silica core, yielding a more suitable coating on a less breakable fiber. There may be a slight difference in extraction selectivity compared to the same coating on a standard fused silica core. 2cm fiber assembly contails no spring.. 24 ga Needle Size. df: 65 µm. Volatiles, Amines and Nitroaromatic Compounds. . . Sigma-Aldrich 57327-U SPME Fiber Assembly for Autosampler, Polydimethylsiloxane/Divinylbenzene, PDMS/DVB, 24 ga Needle Size, Pack of 3. Country of Origin : United States. Part Number : 1196K05EA. Pack of : 3.