SL700 Series

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  • The "SL"

    The “SL” in the part number stands for Safety Lock, which refers to the style of the spring’s end. You’ll see this type of end in the product photo.

  • The "7"

    The first number after the "SL", 7, refers to the gauge of the wire.

  • The Last 2 Numbers

    The last two numbers in the spring code (like “28” or “32”) tell you the length of the spring, measured in inches. So if you see “28,” that means the spring is 28 inches long, not including the end.
Our In-Depth Manufacturing Process

Spring Weight

SL728 = 4.6 LBS

SL729 = 4.5 LBS

SL730 = 4.9 LBS

SL732 = 5.2 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. 

SL728 = 7'0" High

SL729 = 7'0" High

SL730 = 7'6" High 

SL732 = 8'0" High

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 SL70000 Series springs, lengths 28-32 have an intial tension of 110-120 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.