Eterna T4 Tubes made by Eterna are called T4 because they measure four eighths of an inch in diameter (about 12.5mm) they normally have plastic end caps.
The measurements DO NOT include the pins
They are replacement tubes for Eterna brand kitchen light fittings
If your tube is only lighting at each end then it is possible the fitting itself has failed, we have replacement fittings on the website if you need one.
If you don’t see the tube you want then please get in touch as we may be able to help