Deciding on the size of your fenders is an important job. Too big and they will make contact with the water and cause drag. Too small and they will roll up and fail to protect your hull. The size guide here is a general guide and depends largely on the amount of freeboard you have and whether your boat is a motorboat or a sailing boat. If you are still unsure give us a call or drop us an email to firstname.lastname@example.org are always happy to help.