Snark Sail Size Identifier
How to tell the 45 SF and 55 SF sails apart:
Compare height to width of your Sunflower sail. If equal, you have a 45. If a lot taller than width, you have a 55.
Or if you do not have the old sail, compare the two spars (poles) that go into the sail sleeves.
If poles are equal length to each other, get the 45. If one pole is longer than the other, get the 55.