Supa Airline Elbows Twin Pack are the easiest of way to obtain a 90-degree bend in your airline. Avoids kinking in airline tubing should you need to bend your airline around a corner. Made from quality materials that are non-toxic & odourless. Designed to fit airline tubing with an internal diameter of 4mm and an external diameter of 6mm. Part of an extensive range of airline accessories from Supa Ltd Supa have been involved the aquatic trade since 1949, so have built up over many years a vast knowledge & experience of all that is essential for successful fish keeping.