The GRSV45R Refurbishment Slate Vent is designed to be retro fitted into random slated roofs. It can be used for both high and low level roof ventilation requirements. Allows 10000mm2 airflow per vent UV Stablised Polypropylene The hood of the GRSV45R features a 4mm fly screen to prevent blockage from falling debris and entry of large insects into the roof space The GRSV45 has been extensively independently wind tunnel tested to the following standards:- BS 6367 Deluge test 225mm/hour rainfall. Driving rain test down to a roof pitch of 15 degrees with an up roof wind speed of 13m/s. Rainfall rate of 200mm / hour to generate a fine penetrative spray.