This 10w bulb is 338mm long excluding pins and 352mm long including pins. The manufacturer specifies a tolerance of +/- 2mm for these tubes. This is a 10w T4 tube that is 352mm long including the pins at each end. It is used in under cupboard lights and some illuminated mirrors.

T4 fluorescent fittings have been discontinued since 2015 due to EU regulations. The electronics are located in the light fitting and not the tube. If you are finding your lamps are not lasting as long as expected, this would indicate a fault in the light fitting and not the tube - unless the tube is physically smashed it's very unlikely to have a fault. You can test tubes and fittings by swapping tube from another working fitting. Unfortunately manufacturers no longer provide a guarantee for T4 tubes, as the light fittings they are installed into may be approaching the end of their life. These tubes from Leyton Lighting have plastic end caps that can be removed. This makes the tube slightly shorter which can help with installation into some brands of light fitting.