These are internal angles. These internal angles are for use with the PVC trunking. The product is made from hard wearing PVC to guarantee a great product. PVC trunking used should be 38mm X 16mm Internal Angles to insure that everything works well. Trunking is used to insure all wires are neatly and safely tucked away. This will help insure that there are no trailing wires and provide a safer work environment. We have a wide variety of trunking that will allow you to work no matter what your needs are. This 38mm X 16mm internal angle PVC trunking comes with a one year guarantee, as do all of our product on this website electricals247.co.uk.