This module adds a new Better Exposed Filters plugin that allows to filter using a select element for string data type fields.
In general it is better to use taxonomy reference fields for such purposes, but sometimes the current data structure is as is or it's simply easier or better in terms of performance to use a simple string field.
To use set a new operator "In (comma-separated)" on a string field filter and in Better Exposed Filters settings set "BEF Select" for the filter.
Works well with Chosen.