Inner diameter 80mm. Designed to distribute air in the cab or vehicle interior. Supplied in coils of 10m. Call for retail sales.Compatible with Webasto : Air Top 2000 , Air Top 2000 S , Air Top 2000 ST , Air Top 2000 STC , Air Top 3500 , Air Top 3500 ST , Air Top 3900 EVO , Air Top 40 EVO , Air ..