Part# ASC-SH2 Straight Dual Crystal Sensor with Shutter. Fully compatible with INFICON, MAXTEK, SIGMA, or SYCON controllers. 5 or 6 MHz crystals can be used. 1/8" (3.175 mm) water lines are 30" (762 mm)long, along with 1 air line for operation of linear shutter. Use with ASC-FT2 feedthru.