P700 Series

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  • The "P"

    The “P” in the part number stands for Plug-End, which refers to the style of the spring’s end. You’ll see this type of end in the product photo.

  • Insider Diameter

    The first number after the "P", in this case, 7, refers to the gauge of the wire. The P700 Series is the third biggest in the "P" series.

  • The Last 2 Numbers

    The last two numbers in the spring code (like “20” or “42”) tell you the length of the spring, measured in inches. So if you see “20,” that means the spring is 20 inches long, not including the end.
Our In-Depth Manufacturing Process

Spring Weight

P720 = 3.3 LBS

P728 = 4.5 LBS

P730 = 4.5 LBS

P732 = 4.8 LBS

P736 = 5.1 LBS

P742 = 5.7 LBS

Spring Length

The length has nothing to do with the weight of the door, but everything to do with the height of the door. 

P720 = 6'6" High

P728 = 7'0" High

P728L = 7'0" High

P730 = 7'6" High 

P732 = 8'0" High

P736 = 9'0" High

P742 = 10'0" or Higher

Initial Tension

The initial tension is determined by how many pounds of pull force it takes to stretch the spring 1 inch. 

All of our P300 Series springs, lengths 20-42 have an initial tension of 110-120 pounds, except P728L which has an initial tension of 75-85 pounds.

Wire Type

All of our springs are composed of ASTM (American Society for Testing and Materials) 229 oil-tempered wire. 

This specific one-piece extension spring uses 7 gauge wire which refers to the thickness of the wire.

Compatible Hooks

The style of hook is dependent on the amount of springs being used. 

For 1 spring, C-Hooks will be used. 

For 2 springs, W-Hooks will be used.