Most European burner are sized in lignes, indicated with the letter L or the triple prime ‘’’. Lignes are an old french measurement, 1/12 of a French inch or 1/144 of a French foot, 1 ligne equals 2,256 mm. The size of a flatwick is the width of this wick in lignes. The size of a round burner, like the kosmos, matador and Ideal burner is the wick folded double lengthwise in linges measured on the inside. For example a 20”’ round burner has a wick of 20 x 2,256 = 45,12 mm x 2 = 90,24mm – 0,24 = a 90mm wide wick.The width of the wick differs between countries and time period, because the manufacturers wanted people to buy their wicks, and not a cheaper replacement wick. By making burners with a different wick thickness, the ligne differs from one model to another. All manufactures of oil lamps, nowadays and in the past, roughly followed the ligne. But it was more of a guideline than a precise measurement. If you want to replace a wick in your oil lamp and don’t know the exact size and model, you can measure it with a calliper. If you don’t have a piece of wick left, we advise to see a specialist to determine what wick to install. The ligne is still being used by to indicate the size of buttons and by hat makers to indicate the width of the ribbon on a hat. French and Swiss watchmakers use the ligne to indicate the size of the watch movement .