The GRSV45 Slate Vent is designed for use with random slates and has a base size of 600 x 450. It can be used for both high and low level roof ventilation requirements. Alternatively it can also be used as an outlet terminal for extraction fans and soil pipe ventilation when used in conjunction with a Manthorpe GRPA Flexible Pipe. Allows 10000mm2 Airflow Per Vent UV Stablised Polypropylene The hood of the GRSV45 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