HTDU/HTU Detectable Underground Tapes Panduit HTDU/HTU Detectable Underground Tapes are designed to warn buried utility lines. These HTDU tapes are made of detectable laminated aluminum, and HTU tapes are made of polyethylene tapes. The HTDU/HTU tapes are available in rolls of 30.5 meters and multiple colors. These tapes are flame-resistant and RoHS compliant.