Celestron AVX mount is not equiped with a bubble level to start mount setup.
This support enables to fix a bubble level (see model below) on an AVX mount.

Installation:
1) Perform mount levelling as usual
2) Insert support with bubble level
3) Adjust support for correct reading
4) Fix support with glue when adjustement is correct

Bubble level model:
https://www.google.fr/search?q=Multipurpose-2-Way-Spirit-Level-T-Type-Level-Bubble-Horizon-Level&oq=Multipurpose-2-Way-Spirit-Level-T-Type-Level-Bubble-Horizon-Level