Housings have holes for mounting.

A spring controls the tension.

For controlled extension and retraction, these retractors provide the same amount of force no matter how far you extend them. The flexible attachment cable allows a wider range of movement than standard constant-force springs.

Unlike constant-force springs, the farther you pull these, the harder they are to pull. Use them for applications where the load becomes lighter as the spring contracts, such as in automated dispensing machines.