ADCO 36049 White Tyvek 36'1" - 40' Roof Cover Constructed using Dupont Tyvek for maximum durability and UV resistance Water resistant yet breathable Prolongs the life of roof substrate and helps eliminate black streaks Accommodates any common accessories mounted on the roof (Satellite, horns, A/C, etc.) Measure only the length of the RV's Roof to determine size needed (From the very back to the beginning of any slope on the front of the RV)