HDPE pipe during extrusion. The HDPE content is coming with the heater, into the die, then in to the cooling tank. This Acu-Ability conduit pipe is co-extruded - black inside with a thin orange jacket, to designate electrical power cables. Also generally known as "gap flanging", hollow cavities inside extruded https://edgarzqhwk.blazingblog.com/29320455/aluminium-extrusion-no-further-a-mystery