Helps hold the new unglued surround in place so that the voice coil can be properly centered when the surrounds are drying.

Bose 901 drivers are awkward to re-do the surrounds on and get the voice coil properly centered when running a 40hz tone through them. This also keeps the coil centered when the surrounds are drying so they wont shift from movement or the surround's glue not being dry enough to support the coil's position.

Makes restoring the drivers on the 901 sooo much easier and you end up with a high quality job done with half the amount of time and with the amount of drivers the 901 has this can be a great saving.