I'm not sure exactly what you're asking, and others may be able to be more helpful. In the meantime, furlers are usually bought by the length of the headstay/forestay and size of boat. Depending on the make of the furler you want to buy, their websites usually give instructions on how to measure to buy the correct one. Are you replacing your existing furler with the same brand, or going to a different brand--there is quite a variety of styles, and associated cost, so it would be worth doing some research on them first.
If I've misunderstood your question, try again.
Frank
