This extension spring is commonly used with synthetic cable in order to retain tension where the cable path causes slight variances in the amount of slack in the line. The spring has an overall center-to-center distance of 48mm at rest, but can be stretched 32mm for an overall length of 80mm. Each loop end has an inner diameter of just over 4mm so it can easily fit onto an M4 screw. The spring is made from spring-tempered steel to retain its rate and shape over thousands of cycles.
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