This product is a pack of 5 x 13mm barbed elbow connectors to join to our irrigation pipe with an inside diameter of 13mm and an outside diameter of 16mm. All of our 13mm and 16mm connectors are designed for the 13mm and 16mm pipe that we sell. This pipe will have an inside diameter of 13mm and an outside diameter of 16mm. The 13mm and 16mm pipe and connectors that we sell are all the same size, so if you order a 13mm connector and receive a 16mm connector, we have not made an error. If you water pressure is high, we recommend that you use jubilee clips or cable ties on the barbed joints. You can use a pressure reducing valve at the source to reduce the pressure. The item may vary from the picture shown.