BRACKET E-2A is part of the BRACKET E ceiling-and-wall mount distance holder.
The insert allows mounting the AGATE/AOCD-260 devices:
directly on flat surface
on the BRACKET A / BRACKET B holder.
The BRACKET E-6 tamper sensor is mounted on the insert.
The BRACKET E-2A insert can be mounted on the BRACKET E-1 (GY) body.