How to tell if you have a '4.7' sail: The 4.7 is similar to the old 'Standard' sail as it has cross cut panels. Many 4.7 sails also have an obvious 4.7 logo somewhere on the cloth. Next, you can measure the luff (the front edge of the sail along the mast sleeve). This measurement should be about 4080 mm or 160 inches from the top of the sail to the bottom.