Start rolling away re-roofing hassles with Marco's RE2™. No more 1x4's between the existing composition and new metal roof – they can warp, crease the metal, and rot the new roof. Instead of those 1x4's, use RE2™ – a revolutionary high density polyethylene foam, lightweight, yet strong, and comparably priced to wood spacers. It comes in two 150-foot easy-to-handle rolls – just roll it across the old shingled roof, tack it down with the 50 provided nails, and install the metal roof on top. RE2™ acts as a spacer between the roofs, won't warp or corrode, and provides air flow and ventilation.