The Dwyer A-VPX-CKIT Air Cones for Thermo-Anemometers, with Bag optional cone kit comes with a round 7.2 in. (183 mm) diameter hood and a rectangular 10.9 x 8.9 in. (277 x 226 mm) hood. These cones convert a Thermo-Anemometer into an air volume flow balancing tool for use with small grilles and diffusers.