I bought two reasonably priced 18" fluorescent light fittings from Lidl and fitted one above my desk so that I could see the keyboard better. When the bulb blew in the first one I replaced the whole fitting with the second one and ordered replacements. When they arrived they were too long. Checking the tube length with a tape measure revealed that I needed tubes T5 14W but importantly 515mm long cap to cap. Trawling on-line through all the suppliers advertising tubes, the shortest tubes readily available were 549mm long. Eventually I found Bulbs to Go advertising suitable tubes 516mm long, so I ordered two. When the confirmation email arrived it stated 516-521mm. I sent an email saying length was critical anything longer that 516mm was no use. I rang up the following morning - spoke to Heidi. She was very helpful and took my number. She had the stores people measuring the tubes to confirm that the two for my order were 516mm long and later that day rang me back to confirm they were. Two tubes arrived the following day well packed in corrugated cardboard, bubble wrap and cling-film - took 20 minutes to get down to the tubes. I fitted one today and it works fine. Well done Heidi, thank you very much - a great service.