D-SERIES (LA) - LIQUID TIGHT CONDUIT UL LISTED & CSA APPROVED. The flexible inner core is made from a spiral wound strip of heavy gauge, corrosion resistant, hot dipped galvanised steel. The 16mm through to 40mm trade size are square lock formed and include an integral bonding strip of copper that is enclosed within the convolutions through out it’s entire length. The 50mm and 63mm trade sizes are designed with a fully interlocked strip.