The Corodrain B Type Valley Trough is for use with double lap slates and tiles, which are dry bedded. There is a standard (type:HB) and heavy duty (type:BX) option. The valley fixes over the batten for fast and simple installation.ApplicationSuitable for use on roofs with pitches from 17.5 to 55.Can accommodate a maximum difference between two rafter pitches of 15.Designed for use with natural slate, manufactured slate and plain tiles.PropertiesLength: 3m.Width: 330mm.Weight: 1.83kg per m2.Thickness: 1.3mm.Colour: grey / blue.Material: GRP - high quality unfilled polyester resin with glass fibre reinforcement.Valley selection table Roof area less than 25m2 Roof area 25m2 to 100m2 Rafter PitchValley TypeMax. Valley LengthValley TypeMax. Valley LengthMinimum Lap Length17.5-22B / D7m--350mm22.5-29A / B / D7mB / D14.5m300mm30-34A / B / D7.5mB / D15m200mm35-39A / B / D7.5mB / D15.5m200mm40-44A / B / D8mB / D16.5m150mm45-49A / B / D8.5mB / D17m150mm50-55B / D9mB / D18.5m150mm