# Viton O ring, 30mm inner diameter, 2mm cross section

## Details
*   **Material:** Viton or Nitrile
*   **Inner diameter:** 30mm
*   **Cross-section:** 2mm
*   **Outer diameter:** 34mm
*   **Supplier website:** [http://www.simplybearings.co.uk/]

The O-rings function as springs, to provide a return force on the nut that is pulled upwards by the screw.  I use Viton O-rings, 30mm ID, as they provide about the right force.  You can substitute for rubber bands, but it's difficult to specify the size directly, and they tend to perish and snap in a few weeks.  Viton O rings are well worth the effort and price!



