Flexes are available with 2 or 3 cores (conductors). 2 core flex is only suitable for appliances that don’t need an earth connection (marked ), and should not be used for extension leads with 3 pin sockets or plugs.

2 core flexes are available in both round and oval shape. Oval (flat) uses less material, but any twisting of the flex is visible, whereas it isn’t with round.