TSI 9565-X VeloiCalc Multi-Function Ventilation Meters are portable, handheld, Multi-Function Ventilation Test Instruments featuring a menu-driven user interface for easy operation in your local language. On-screen prompts and step-by-step instructions guide the user through instrument setup, operation, and field calibration. The TSI Alnor 9565 Series ( 9565, 9565-X, 9565-A, 9565-P ) also feature an ergonomic, overmolded case design with probe holder and a keypad lockout to prevent tampering during unattended use. These instruments are available with or without a differential pressure sensor and are designed to work with a wide range of plug-in probes. The TSI 9565-X does not come with any probes.