A new more efficient kind of fluorescent tube has been developed. The new tubes are called T5's whereas the old are T8's.
All new facilities should specify T5 as they use up to 40% less energy than the equivalent T8 and give off 10-15% more light! This is achieved by a better performing tri-phosphor coating.
T5's are thinner and shorter than their equivalent T8's, so they will not fit into the existing T8 socket and light fitting. You will need a T8 to T5 conversion kit to do a simple change over without requiring an electrician to replace the fitting.