How to select the correct sprin, Step 1 is to measure the wire diameter. To do this you will need to measure 10 coils then compare that measurement to the chart below to see the wire size,double check by measuring 20 coils and compare to the 10 coil measurement, if the 2 measurements do not match, try measuring in a different area of the spring and also make sure the spring is not stretched. Do not measure in the ends where the cones are, the cones stretch the ends where they are installed.(Table detail in picture No.3) Step 2 is to determine the spring inside diameter, if the spring is broken you can simply use a ruler to measure the inside of the broken end, if the spring is still in one piece you can measure the outside and deduct the wire size X 2. You also may be able to find stampings on the cones which will help determine the ID, ( P200 or P2000 for 2” and P175 for 1 ¾”) The most common sizes in residential springs are 1 3/4" and 2" ( Raynor doors use 2 ¼” ID )Step 3 Step 3 is to measure the length of the spring, Measure the spring only, not including the winding and stationary cone. If the spring is broken measure each piece and add the two measurements together to get the total length. If the spring is still in one piece and wound, it will be longer by 2-3” then when it is relaxed.the proper way to measure is to unwind the spring to measure the correct length.Step 4 is only important if ordering a single spring, determine the wind direction of the spring, ( right hand wind ( RW) or left hand wind (LW). Below is an example of the different spring winds. This is probably the most confusing part of the spring ordering process, as The RW is normally on the Left side and the LW is normally on the Right side. Be sure to check the wind direction and not make assumptions. If you look at the end of the spring and compare to the picture below, you will be able to determine the correct wind direction.(Picture-4-5) (ST0208308300SN30