You need to know the Diameter (Ø) in cm, and the Total Height / Length in cm of the fender from end to end (including the Eyes).
Often boats have a mix of fenders, so it is important to measure each one individually before placing your order.
The easiest method is to measure each fender with a tape measure and record the dimensions. First measure the Diameter “D” (cm) of your Fenders (or with a tape measure around the Circumference, then D = Circumference / 3.14). Then measure the Total Length / Height (cm). Note: measurements need not be precise.
Alternatively check the Fender manufacturer’s catalogue. You will often find the Manufacturer Name and Model Reference embossed on near the Eye. However, product dimensions can change slightly from year to year even for the same Model Reference.
As Covers are designated knitted with 2-way stretch (in the Diameter and in the Length) to allow stretching in both dimensions, the Cover sizes are designed to work with a range of Fender Diameters.
