"It states that these tubes are 218 mm long. But that depends where you measure them to. They are 218 mm long on the tube but that does not include the prongs. Thus they are longer than 218 mm. and don't fit in other manufacturer's linkable striplights. I thought all T4 6w tubes were the same length! The Robus linkable striplights we have take a tube that is 218 mm long including the prongs! So these tubes are no use at all unless you use them on Halolite fittings!!!!!!!!!!!"