uPVC 350mm Vented Soffit Board (10mm General Purpose) 5m - White Dimensions Length: 5m. Width: 350mm. Thickness: 10mm. Material: uPVC. Guarantee: 20 years. Description The range of pre-vented general-purpose boards (GPBV) is a popular choice for soffit applications with a line of built-in ventilation along the length of the boards. GPBV products are 10mm thick and are available in widths of 100mm to 600mm. The wider products are particularly useful for deep soffit applications. GPBV products are available in white and a range of woodgrain finishes.