The SPK1 Pocket Knife Style Thermometer features a sharp tip for punching through flex duct and hangs easily from a vent or thermostat. Pull out the probe rod just like you would a pocketknife. 16 detent position grooves hold the rod at virtually at any angle. The probe rod folds away simply with no cover sleeve to lose. Temperature range: -58 to 392 deg F. One of our most popular instruments for HVAC/R field service.