Constructed from PTFE with AISI 304 steel retaining tab. For glass viscometers of the following models: Cannon-Fenske for transparent liquids. Cannon-Fenske for opaque liquids. Ubbelohde. Ostwald. BS U-tube. Cannon-Manning semi-micro. Ubbelohde type BS/IP/SL, type BS/IP/SL(S) and type BS/IP/MSL. DIN Ubbelhode.