Our black flexible duct is used for ducting all kinds of electrical installations with a voltage rating up to 500 volts. It is available in a range of coil diameters from 40mm up to 110mm. These measurements refer to the outside diameters (O.D.), all dimensions can be found in the table alongside the product image.The ribbed external wall ensures that the duct can withstand high compressive forces whilst the smooth inner bore resists any snagging.You should choose a diameter that allows plenty of room within the duct to allow the cable or cables to be drawn through smoothly. All full coils come with an integral coupler and a pre-installed draw cord. The coupler enables two coils to be connected together as required.The length of this coil is 50m.